How Can a Second Defender Make Themselves Useful?

Marking additional targets

Most defenders can only effectively mark some enemies in a typical fight versus five opponents. In fact, in such a scenario, few defenders actually want to be ganged up on entirely. This is in part because even for a defender, focus fire can be dangerous. Just as importantly, even if a defender can endure focus fire for any given encounter, such a strategy runs the risk of draining the defender's healing surges quickly. If an adventuring day has to be cut short because the defender has no healing surges while the rest of the party is uninjured, then something has gone wrong. In such a situation, the party benefits by having some attacks directed away from the defender onto other party members.

A second defender helps admirably in this regard. In a typical combat, it is entirely reasonable for two defenders to each mark one or more targets, effectively splitting their enemy's attacks and making the "focus fire on the defender" strategy less viable for enemies. Moreover, it allows the party to draw from the healing surges of at least two of its members, extending the adventuring day.

Note, however, that this strategy is not viable for fights against a smaller number of opponents. Clearly, it is not possible for both defenders to mark a single solo. Against an encounter of two elites and some minions, defenders may also run the risk of stepping on each other's toes, because if one defender is substantially tougher than the other (or tougher against that specific kind of enemy through resistances or otherwise), it may in fact be best for the primary defender to draw fire from both targets.

In this situation, it is very important that the secondary defender is not left standing around with nothing more than a measly longsword attack to contribute to the fight. Thus, off-tanks need to have additional capabilities with which to make themselves useful. Some suggestions for this are given below.

Punishment without marks

Although many good defender-oriented powers are mediated by marking, not all are. This is extremely important for off-tanks, as it allows them to punish a solo for attacking their allies, even if that ally is themselves a defender and has already marked the solo!

Remember how I said that defenders operate via a lose/lose dilemma? Well, mark-less punishment powers allow two defenders to combine their lose-lose dilemmas additively. Allow me to illustrate how this might work, typically. A party including a hammer and board fighter and a greatweapon assault swordmage fight a solo. Both the defenders in question are relatively durable. The fighter marks the solo, while the swordmage gets ready to interrupt the solo's first attack with the Reaper's Challenge level 15 daily power. The solo is now faced with the following options (leaving aside close blast/burst powers for simplicity):

1. Attack the fighter. This is bad for the solo because the fighter is the most tough member of the party, and the swordmage will unleash her Reaper's Challenge upon the poor critter, thus causing any attacks to deal half damage.
2. Attack the swordmage. This is bad for the solo because the swordmage, though perhaps not quite as tough as the fighter, is still a defender and is therefore pretty durable. Moreover, the attack will suffer the full effects of the fighter's punishment capabilities - most likely a combat challenge attack and/or a combat superiority-boosted opportunity attack, followed by a -2 on the attack roll.
3. Attack another party member. This is bad for the solo because although the other party member is likely to be much squishier than the swordmage or fighter, it will be punished twice for its troubles. In this scenario, the solo would cop the reaper's challenge weakening effect, and the -2 penalty and melee basic attack from the fighter.

While a single defender poses their marked targets with a dilemma between two bad options, two defenders working in concert pose their marked targets with a difficult lose/lose/lose scenario -attack one defender, attack the other defender, or attack somebody else. I dub this the off-tank's trilemma. In order to effectively assist your defender ally in tanking a single target, you must make all three options sufficiently unappealing for your target.

What Not to do as an Off-Tank

Overwriting the Other Guy's Mark

If you are aiming to help another defender, rather than replace them, it is very important that both of you avoid powers and feats that hinder each other's defending. Unfortunately, some of the best marking powers are not particularly selective, and therefore may not always be ideal when working alongside an ally. A few examples below:

Nature's Wrath - UPDATE: Actually, Nature's Wrath has been clarified in the Warden Essentials article in Dragon 379. You can choose to exclude any number of enemies from Nature's Wrath, so wardens aren't screwed for cooperative tanking.

Contagious Challenge - The contagious challenge feat can potentially overwrite an ally's mark. If your Divine Challenge target is adjacent only to a target marked to your ally, you will need to choose whether to attack something else instead or to overwrite your ally's mark on a hit. This may be a particularly difficult choice if it isn't possible for you to otherwise engage your divine challenge target.

Warrior's Challenge (Fighter enc 17), Call of Challenge (Paladin util 2), Majestic Halo (Paladin daily 1) and others - all potentially problematic, if both defenders intend to use marks.

If one defender is confident that they can operate without the use of their mark, or are happy to reapply their mark when necessary, this may not be too much of a problem. Nevertheless, it is a difficulty that a two-defender team must address if they are to work together effectively.

Getting too Competitive

A bit of healthy rivalry between strikers can often be a good thing. Damage-dealing is fairly additive most of the time, and two strong strikers in a party of five is pretty ideal really. Defending isn't necessarily the same. Sometimes, there's only one foe to tank. When two players decide to make defenders that focus purely on being "main-tanks" with no consideration of teamwork, it can lead to one of those defenders being redundant during solo encounters. That extra defender could have been a controller or striker, and nobody likes feeling like a liability.

Thus, it is important that off-tanks take heed of the other roles they can fill, or make sure that they have some mark-less punishment abilities available when there aren't enough tankable foes to go around. Moreover, it is important that off-tanks play it by ear as they level. If you find yourself only using that divine challenge every second encounter, or you find that anything you challenge always attacks you anyway, avoid spending more resources improving it further. Instead, you might want to consider investing in more feats or powers that boost your other capabilities or your durability. If you find that your enemies ignore your marks then you might want to make yourself more punishing. Consider trading that sword and board out for a fullblade so that you can assist in dealing damage. Alternatively, you could enhance your marking capabilities through feats or power choices, or pick up some mark-less punishment powers. This is all advice that single defenders can benefit from - but it applies doubly to off-tanks because it is much easier to overdo it.

In fact, it may be that some of the best duo-defender combos involve two "off-tank" builds working in concert. If they work cooperatively and both choose one or two mark-less punishment abilities, they could be far more effective than a single defender, yet both simultaneously function effectively in a second role. For instance, my half-elf bard/paladin is currently working alongside an eladrin feycharging swordmage. We work pretty well together, but the bard happily covers the leader role, while the swordmage zips around the battlefield making numerous attacks each round with her fullblade.

Commentary on Classes, Powers and Feats

This section is largely a work in progress, but I'll try and write a short commentary on each class' potential eventually. Please assist me by suggesting any important off-tank stuff I've missed and I'll try and include it as soon as I have time!

I've made a point of including every mark-less punishment ability that I can find in each class entry.

I've omitted:

• Marking powers because they are covered amply by other guides and because although they are good for any tank, two tanks cannot both mark the same target and thus it is adviseable for off-tanks to take a close-look at mark-less punishing abilities. 
• Powers that punish enemies for making any attack, or provide defense bonuses to your allies and yourself, as they do not have any particularly interesting synergy with a defender's toughness, so I've saved myself the space!
• Purely self-defensive powers. Although potentially very useful, I figured that the worth of such powers was relatively self-evident. Moreover, I think that it is easier to make a character tough than it is to make them sticky (usually all it requires is wise ability score allocation and a few feats), so I've focused on powers that make off-tanks stickier here.

Artificer

Runes of the Shadow Tendrils (Daily 29, EPG): If you cast this on the other defender and can use positioning (e.g. flanking and opportunity attacks) to prevent the one or more of the targets from attacking anybody other than yourself or the other defender, then this will function similarly to Reaper's Challenge.

Avenger

Merciless Nemesis (Avenger daily 29, DP19): Used by a Pursuit Avenger against the target of a defender's mark, this power potentially forces your enemy to either attack your high defenses and suffer the ill effects of your defender buddy's mark, or shift and charge somebody else and suck up your censure of pursuit damage the next round.

Bard

Bards make great leaders but also bring a number of things to the table in building an off-tank. Perhaps most importantly, Bards can multiclass into any number of classes through their multiclass versatility class feature. Bards also have strong buffing, positioning and controlling capabilities. They have middling hit points and surges along with a modest but serviceable array of initial proficiency feats. For three feats a bard can be toting full plate, a heavy shield, and a songblade longsword. With toughness thrown in, a valorous bard is a tough enough cookie to get the job done.

Bards naturally synergise with the paladin class, which is one of the better defender classes to multiclass into. Multiclassing into bard can bring a daily heal and the potential to pick up some useful control or leader powers, but is unlikely to boost an off-tank's tanking capabilities directly.

War Song Strike (at-will, PH2 69) - This power is secretly an off-defender power. It allows you to keep everybody apart from yourself topped right up with temporary hit points, thus penalising enemies for attacking those targets. On the other hand, there are perhaps better bardic at-wills, even if they aren't particularly off-tank oriented, such as Guiding Strike and Vicious Mockery.

Shout of Triumph (encounter 1, PH2 69) - This is just one example of the numerous ally-friendly forced movement powers that bards have at their disposal. Powers like this can make a huge difference when used strategically with your own, or another defender's mark.

Chord of Resilience (utility 6, AP 9) - This performs very similarly to a once per encounter Aegis of Shielding during lower levels, but does not require you to mark the target before you can use it. You will get an opportunity to use this power every encounter - do not underestimate that fact about it. However, it does not scale particularly well and might not be worth keeping beyond about mid-paragon tier.

Scorpion's Claw Strike (encounter 7, PH2 72) - Quite a good power for an off-tank as it makes attacking your defender ally unpalatable, whilst simultaneously allowing you to put that ally in a flanking position so that it is difficult for your enemy to shift and charge away to anybody but you or him. That is, of course, assuming that you don't have any other melee allies nearby!

Illusory Erasure (utility 10, PH2 72) - This power functions very similarly to Scorpion's Claw Strike except that the slide is perhaps a little more flexible and invisibility effectively grants a +5 to all defenses against most attacks. Lastly, it's a minor action and the effect isn't reliant upon hitting - yay!

Mocking Epigram (daily 19, AP 14)- A pretty decent mark-less punishment ability. On the plus side, it can really hurt enemies that make multiple attack rolls per round (provided that there are other enemies around for them to hit). It also really hurts enemies whose attacks impose status effects, as those are transfered by the power too! On the more negative side, the power is save ends. Therefore, it is probably best to use this one on normal or elite artillery/controllers, because it might not last long versus a solo.

Fighter

Fighters make excellent defenders in general, and the class has plenty in it of worth to an off-tank build. Starting off with fighter as the base class gives you very good hit points, surges, and proficiencies, meaning that you will need to spend relatively few feats on durability. Combat Superiority buffs your opportunity attacks significantly, which is great for an off-tank because opportunity attacks can come into play even against enemies marked by your ally. Combat Challenge is a strong marking mechanic, and has the added convenience of being optional - you don't have to overwrite your ally's mark whenever you hit their target! Unfortunately, the punishment mechanic is only effective against adjacent targets so it is a bit more difficult for fighters to have fun with advanced kiting tactics. Not to worry though; different strokes for different folks.

Fighter also makes a very good class to muticlass into. It has a strong selection of feats, some of which are almost obligatory for certain builds. If you have a decent strength score, seriously consider multiclassing fighter for power swaps. In fact, some of the fighter dailies are stances and are not dependent upon strength, so are worth taking a look at regardless.

Brash Strike (at-will, MP 7) - Though perhaps not strictly speaking a defender-oriented power, it is nevertheless a pretty good choice for an off-defender as the cost you pay for striker-level damage (granting combat advantage) is somewhat mitigated by your ally's mark and your very high defenses.

Footwork Lure (at-will, MP 7) - One of a few forced movement at-will powers that can be a good mainstay for a polearm gambler.

Dual Strike (at-will, MP 7, but check errata) - A great way for single-classed/hybrid Fighters to mark two foes at a time. The utility of this power will depend somewhat upon the arrangement you have with the other tank - how are you divvying up marking rights? It is good damage too.

Tide of Iron (at-will, PH 77) - A solid positioning power.

Hounding Longarm (daily 5, MP11) - this power provides an encounter-long mark-less punishment effect against a single foe that is similar to combat challenge but grants a shift in addition to the melee basic attack. That extra shift is key, because it largely negates the all-too-common shift+charge strategy that your opponents will often use against you. The only limitation is that you must be using a reach weapon to use this power. I knew it sounded too good to be true!

Pinning Smash (daily 5, MP 11) - If the other defender is able to tank at a range, hit a melee enemy they've marked with this power and tell all your allies to stay out of reach. Your foe won't be able to attack anybody but you, and will therefore suffer the full effects of your ally's mark.

Vigilant Protector (util 6, MP 12) - A stance that buffs the AC and Reflex of adjacent allies but reduces your own. If you're a dragonborn, have a few melee allies, and/or intend to keep the other defender close, this might be worth considering at least.

Savage Parry (encounter 7, MP 12) - A decent interrupt that deals a modicum of damage, gives you some temporary hit points, and reduces the damage of the triggering attack. It's arguable whether this is really better than a combat challenge melee basic attack, but this power is useable even when you haven't marked the target.

Phalanx Leader (utility 10, PH Heroes 1) - A neat little encounter buff. Keep in mind that it is dependent upon positioning and that the AC bonus is a shield bonus.

Stalwart Guard (utility 10, PH 81) - a daily stance comparable to Phalanx leader, with comparable strengths and limitations. Phalanx leader may be slightly better if used judiciously.

Defender's Gambit (daily 15, MP 16) - Something like this might be worth considering as an off-tank. If the target is marked by your ally, they may have a hard time deciding whether to take that free attack or not.

Interposing Shield (utility 16, PH 82) - Good for when you're off-tanking without using your mark, but like all fighter shield powers it has a range of 1.

Tap and Counterstrike (encounter 17, MP 17) - A pretty decent mark-less punishment power.

Strike of the Watchful Guard (Fighter daily 19, PH84) - grants you an encounter-long mark-less version of combat challenge against the target. As icing on the cake, the melee basic attack it grants is a free action rather than an immediate interrupt. This power can therefore trigger multiple times per turn.

Turnabout Riposte (encounter 23, MP 20) - A great mark-less punishment power, but less compelling if you generally have targets marked because it uses your immediate action.

Battle Awareness (class-specific multiclass feat, MP149) - Allows you to interrupt an enemy's attack against one of your allies once per encounter, even if the ally had marked that enemy. Combine it with the Eldritch strike power or the Mark of Storm feat combined with a lightning weapon. In such cases, the feat power can be used to invalidate an enemy's attack entirely.

Battle Acumen (paragon multiclass feat, MP 149) - A really nice feat. Unfortunately, you have to paragon multiclass to get it. It's probably not role-defining enough to be worth making such a high sacrifice for, except perhaps if you are a half-elf and want to cherry-pick the best powers from each class. For most other classes it might just be worth it to make a (hybrid) fighter instead.

Fey Charge (paragon feat, MP 143) - I mention this feat because its existence makes MC Fighter an absolute must-have for any Eladrin Assault Swordmage (which itself is an important off-tanking build).

Polearm Momentum (heroic feat, MP 138) - This feat is great for polearm gamblers of any class, making MC fighter a great choice for them.

Phalanx Warrior (paragon feat, MP 144) - Flavor-wise, perfect for an off-tank build. However, there are two limitations with this one you have to consider. First, it's a shield bonus, so it doesn't work if your ally already has a shield. Secondly, the positioning limitation is rather severe. Thus, the worthiness of this feat depends upon your party make-up and battle plan.

Paladin

Since the release of Divine Power, paladins make sweet tanks. They have more base healing surges than any other class, good hit points, plate and heavy shield proficiency, and a marking/punishment mechanic that can be maintained at a range if you have a ranged attack. Other than being ranged, Divine Challenge is also unique in that the punishment part of the power costs no action. Thus, paladins have a surplus of immediate actions with which to do whatever they like. Paladins have a few absolute stand-out powers for off-tanking, described below.

Paladin is a great class to multiclass into in order to make your character more sticky. Soldier of the Faith, the class specific multiclass feat, gives you a full use of divine challenge once per encounter, which combines a mark and a punishment mechanic. It is also possible for a multiclass paladin to pick up feats or powers that utilise the Divine Sanction effect in order to gain additional marking capabilities.

Ardent Strike (at-will, DP 83) - grants you a 1[W] attack that subjects your target to divine sanction (but only on a hit), that can also be used on a charge. May allow certain builds to gain access to a mark that they otherwise couldn't have, but if you have divine challenge you might find that you're often using your standard action to attack the target you've marked anyway, and so might not get quite as much out of the power as you might expect.

Forbidding Strike (at-will, Divine Heroes 2) - this is one of the few at-wills in the game that is ideally used by an off-tank. Provided that you and the other defender are able to flank and sequester your chosen foe away from any other allies, you can provide a mark-less lose/lose dilemma to your enemy every round that you hit with this power. Not bad at all.

Virtuous Strike (at-will, DP 83) - A good way for paladins (or half-elves) that don't use strength for their powers to gain a charisma-based MBA. It does radiant damage, which can be great depending on your DM's preferences, and gives a bonus to saves (which is ok, I guess). Eldritch Strike may be better, so if you are a half-elf you may want to consider taking that one instead.

Shielding Smite (encounter 1, PH 92) - Buffs one ally's AC. Combined with careful positioning and used to buff your ally that has marked the target, can be useful for an off-tank.

Call of Challenge (utility 2, DP 85) - A great way to mark a whole bunch of foes. You may annoy the other defender if you overwrite their mark though!

Avenging Smite (encounter 3, DP 85) - A 2[W] attack to the back of the head might teach your foe not to turn its back on you! Unfortunately, I'm not really sure what the immobilize effect is supposed to accomplish, as it may expire before the target gets another opportunity to move anyway. Still, the immobilize might be occasionally useful. Moreover, it is mark-less punishment and can stack with Divine Challenge damage.

Hold Fast (encounter 3, DP 85) - A strike similar to Avenging Smite which is used as a standard action or in place of a basic attack. The immobilize can be used to halt enemies' movement with an opportunity attack.

Benign Trasposition (encounter 7, PH 94) - A pair of defenders with ranged marks could use this power to switch places with each other, potentially blocking enemies' access to the PC that marked them.

Ray of Reprisal (daily 9, DP 88) - A once-off mark-less punishment. The effect isn't bad although you may feel that it doesn't do quite enough for a daily.

Righteous Indignation (utility 10, DP 88) - A decent enough little buff that allows you to punish an enemy for attacking your ally without having marked them beforehand. It feels a little so-so for a daily though!

Eye for an Eye (encounter 13, DP 89) - A nice ranged, mark-less once-off punishment in response to an enemy attacking one of your allies. A pity that it isn't an interrupt, but it is still pretty nice.

Censuring Radiance (encounter 23, DP92) - a pretty good option. A melee [W] attack targeting fort and weakens the target for any attacks that do not include you as a target.

Demand Respect (encounter 23, DP92) - The big brother of Price of Cowardice and Eye for an Eye, this mark-less punishment power allows an off-tank to blind, knock prone, and deal radiant damage to an enemy as an interrupt in response to their attack against an ally. As it is an interrupt, this will result in a -7 attack penalty for the triggering attack.

Martyr's Smite (encounter 23): Martyr's Strike allows you to redirect damage the target deals back to yourself. Used indiscriminately, this power isn't particularly great, but saved for a key moment (such as when the other defender is low in health and may be dropped during the next round) it might be useful. Note however, that this power is overshadowed by not one, but three other off-tanking paladin encounter 23 powers - Censuring Radiance, Demand Respect and Sublime Transposition.

Sublime Transposition (encounter 23) - This power gives you some pretty good repositioning capabilities, buffs the other defender's defenses, and allows you to follow up with an attack. Not a bad power for an off-tank build at all, though Demand Respect is probably better unless you are immediate action starved.

Discipline the Unruly (daily 25, DP93) - This power gives you a fantastic mark-less punishment ability that applies to any enemy within 5 squares of you! It is a sustain minor, which can be a pain, but it is nevertheless a very good choice for an off-tank.

Sorcerer

Swordmage

Most swordmages function by using their encounter-long Aegis power on an enemy and then using both toughness and positioning to make themselves hard to reach. This tactic is expandable to two swordmages (or a swordmage and a paladin), where each defender blocks the other defender's mark, thus allowing both defenders to kite their respective marks.

Multiclassing into swordmage will only make you a more sticky if you are willing to paragon multiclass. Paragon multiclass swordmages can spend a feat to gain a once per encounter use of any one Aegis, which is fairly nice. It may be a viable option for tactical warlords.

Dimensional Warp (utility 2) - with a paltry minor action, this ability can dramatically alter the course of a battle. Both defenders should mark their targets, and then the swordmage can use dimensional warp. Ideally, this will make both defenders difficult to reach by their marked foes, thus amplifying the lose-lose scenario that the enemies are faced with.

Dimensional Vortex (encounter 3, AP53) - What a great power for an off-tank. Provided you hit, you completely nullify an enemy's attack and can even make them take a swipe at another enemy. Save it for rounds in which you're unlikely to make Aegis interrupts.

Incendiary Sword (encounter 3, Dragon367) - Not a bad way to offtank. if you work alongside a character with an area of effect mark (e.g. Call of Challenge), it could be pretty nice. Five damage isn't a huge disincentive, though.

Energy Theft (daily 5, AP54) - Against a foe that focuses on a particular element, this may be a decent off-tank power.

Enervating Slash (daily 5, AP55) - Not bad at all, apart from the (save ends) part!

Dazing Rebuke (encounter 7, AP55) - This one is not all that good. The enemy has already made at least one attack on their turn when the daze kicks in, so unless they were going to make additional attacks (or opportunity attacks), you probably won't achieve a whole lot with this.

Arcane Deflection (daily 9, AP56) - This power uses an immediate action, so does not work well in conjunction with your Aegis. However, if everything is already marked by the other defender, it becomes very good. Just make sure that all your allies remain adjacent to you or otherwise out of reach!

Silverlight Strike (encounter AP58) - Very nice. Your target grants CA to all your allies, and gains a -5 penalty to hit on all attack rolls vs. them! Guess who it'll want to attack?

Dimensional Slash (encounter FRPG13) - Has some interesting possibilities. Have your ally mark the target and then whisk it away into a corner with you.

Reaper's Challenge (Swordmage daily 15, dragon372) - This lovely daily allows you to weaken an enemy as an immediate interrupt when they attack an ally - even if that ally has marked the opponent. Even better, it slaps on an encounter-long mark-less punishment power - if the target makes an attack not including you, it is weakened until the end of its next turn.

Eldritch Chains (daily 15, AP58) - Not bad. Very dependent upon the positioning of your allies.

Surprising Transposition (encounter 17, AP59) - Very similar to Dimensional Vortex.  In other words, very nice.

Ward of Scales (daily 19, AP60) - A decent daily for an off-tank. Versus a solo, you can use it on your defender buddy to make things interesting. With flanking and careful positioning, the solo may have to decide between attacking you and the defender that has marked it.

Sword Duel (daily 25, AP62) - Quite a decent off-tanking power. 10 damage is not huge at level 25, however.

Sword Chaser Assault (encounter 27, AP63) - Pretty decent mark-less punishment power overall.

Warlord

A Rock and a Hard Place (Warlord daily 5, MP106) - this power was outright designed for use by an off-tank. Provided that you can use positioning (such as flanking) to make it difficult for the target from being able to shift and attack/charge one of your other allies, your enemy will be faced with a lose/lose scenario (as the power's name implies).

Denying Smite (Warlord encounter 13) - If you flank an enemy with an ally that has marked it, using this power may make it difficult for your target to attack anybody but you (unless it has above-baseline mobility). This will hopefully lead to the target attacking your high defenses and copping the brunt of your ally's mark and punishment mechanic.

Exhorted Counterattack (Warlord daily 19): Not only does your target's attack against your defender ally trigger a heal on that ally, but your ally is given an opportunity to retaliate. Not bad, although it is a once-off - something like Reaper's Challenge may be better because of its duration.

Defy Death (Warlord daily 29): An effective once-off punishment mechanic. For an off-tank character, it will be useful against solos (where the other defender has the target marked) but even more useful against a group of enemies, as it could be used to move away from a target you have marked as well, which could potentially make things very hard on your mark during their next turn. 

Multiclass-Only Classes

Noble Indoctrination (Multiclass path, Channel Divinity:Bahamut article, dragon 378) - This multiclass path provides a feat power called Righteous Judgment, which I find hard recommending using over an at-will, but more importantly, it opens up some fairly nifty power swaps. Hand of Justice is a rather good encounter power that damages an enemy for attacking an ally, and allows the ally to spend a healing surge. It's an area attack so will provoke opportunity attacks though. Righteous Savior is a pretty good utility power, bolstering an enemy's defenses and granting you movement when as an interrupt when an ally is hit by an attack. However, these options will use up your one multiclass choice, which may not be a good idea if you are not already a defender (or able to take multiple class-specific multiclass feats for whatever reason).

Platinum Revelation (Multiclass path, CD:Bahamut article, dragon 378) - a more melee-oriented alternative to Noble's Indoctrination. The power granted by the initial feat is OK (comparable to the paladin's enfeebling strike at-will) until epic tier, where it falls behind slightly due to lack of scaling damage (and less reliance upon at-will powers). Dragon's Rebuke is a melee strike that allows you to push an enemy if they then attack your allies, but only as a reaction (so it can only really foil the second and consecutive attacks of multiattack powers). Righteous Intolerance and Zealous Fury, the daily attack powers and utilities, grant you free movement and your allies healing when your enemies attack them. All-in-all, a fairly good multiclass path for an off-tank.  

Paragon Paths

Half-elf Emissary (Bard PP) - both the level 11 action point feature and the level 20 daily give allies a bonus to defenses. This punishes enemies for attacking your allies in a similar manner to a mark, but without actually applying a mark. It is, on the whole, a leader paragon path, but its applications for a leader/off-defender are worth mentioning.

Faithful Shield (Paladin PP) - This path is well suited to an off-defender as every feature and power grants bonuses to AC to either allies or yourself and allies. Some of the features are a bit annoying though - for instance, the +2 bonus to defenses from Sheltering Hands only lasts until the start of the target's next turn, so you might want to delay until right after your ally in order to put it to good use. Defensive Presence is good if your defender buddy is a dwarf or if you have the Swift Recovery skill power.

General Feats

Psychic Lock (Paragon feat, PH205) - this controller feat deserves a mention primarily because it is so good. When the attack penalty is stacked with your own or your wingman's mark, it becomes quite nasty. Have all your attacks apply this penalty with a Githyanki Silver Sword or pick up an at-will such as Vicious Mockery, Illusory Ambush, or Eyebite in order to make use of this.

Thanks for that Chimera - I hadn't really looked closely at the power selection for Warlords. I had a quick look and they definitely have some powers with great potential - I've added a few of the choicest powers into the guide. Tell me if you think I've missed any important bits!

So far, I've avoided adding classes such as warlord, bard or cleric into the "2nd defender builds" section, seeing as those classes don't by themselves have a reliable marking mechanic. Although warlords and clerics do have a few encounter powers that mark at their disposal, I'm trying to draw a line between classes that have just one or two encounter powers that mark, and classes that can mark for at least a few rounds and can back up that mark with a punishment mechanic of their own.

That said, I think that just about any of the leader classes could make a solid foundation for an off-tank build, provided that you gave them feat and power choices to match and perhaps multiclassed appropriately (e.g. Soldier of the Faith or PMC Swordmage could really work will with a cha/int warlord respectively!).