Armor Class

Why is the base armor class "10"? It seems that someone swinging a sword would have a greater than 50/50 chance of hitting an unarmored opponent -- even if there were no Dex bonuses.

One of the realizations I've come to in the last session, was that the players are just too hard for monsters to hit without some kind of inflated bonus. A lot of creatures (goblin, hobgoblin, orc, and kobold) all have bonuses to hit that do not reflect any actual stat -- +3 thru +5 generally. And it seems like this could be resolved by reducing PCs armor class -- and the easiest thing to do here is to reduce the base armor class.

I am thinking about making the base AC 5 instead of 10. Though, might go to a 6 or 7. Of course, this goes both ways, but would eliminate the need for monsters to have an "+3 bonus to hit" for no reason.

So, before I house-ruled such a thing, I wanted to know a) what others thought of reducing the base AC and b) why this was selected as the base AC, anyway. 

Thanks!
It's that way because, as you said, that makes it a 50% chance to hit with no bonuses on either side, and that's how it's intended. The attack bonuses are meant to give you a greater chance to hit and defense bonuses a greater chance to avoid attacks, but without any modifiers there is not supposed to be any statistical weight on either side. It's not realistic, but it's one of those necessary abstractions that make the game function really well.

The reason you don't need to heal up constantly throughout your adventuring day is because of that 50% base; it's also the reason even monsters with very little HP can still pose a threat. So it stands to reason that if the base gave an advantage to the attacker, the game would be very unforgiving, and the outcome of a battle would depend largely on the initiative roll.

I'm a big fan of this system. By making the base at exactly 50%, it doesn't matter how big or small the bonuses to hit and to AC are, as long as they are comparable to each other.

Another reason is that if we lowered the base for enemy AC (which we have to do because PCs can face enemies with PC classes), then we'd have to eliminate the attack bonus granted to martial classes. Then, we would either have to give casters a weapon attack penalty (which I don't think makes sense, because you don't get worse at fighting just because you studied magic, you just don't improve at it the way a warrior does in his training), or leave them at the same attack bonus (which doesn't make sense, because training with weapons does make you better with them than studying spellbooks would).

So, either we grant an undue advantage to the attacker in all cases, or we dramatically alter the power balance between classes, or we make determining enemy AC and bonuses really confusing. I think the base of 10 is perfect just the way it is.
All fair points, but how do you deal with some creatures needing bonuses to hit? For example, the orc gets a +5 to hit with their melee weapon. There seems to be no reason that the orc gets this bonus other than to fix an unbalance of power.

Thoughts? 
Just to nitpick: its 45/55 in favor of the attacker.
Just to nitpick: its 45/55 in favor of the attacker.



That's right, ties go to the attacker.
All fair points, but how do you deal with some creatures needing bonuses to hit? For example, the orc gets a +5 to hit with their melee weapon. There seems to be no reason that the orc gets this bonus other than to fix an unbalance of power.

Thoughts? 



2 of it is the Orc's Strength modifier, all creatures add Str or Dex to melee attacks, so that would remain even if they lowered armor classes (another potential problem to consider). As for the other 3 points, that might be too high, I've long felt that many monsters have too much attack bonus. Since they don't tell us what the other 3 is, I can't say if it's fair or not, but I think that a low level monster like that shouldn't have more than a +1 weapon attack bonus, since a 15 is supposed to be a pretty good armor class in this game, but it often amounts to just negating the enemy attack bonus right now. It could be a holdover from the older packet where Fighter weapon attack bonuses started at +3.

@Keendk, you're right, I failed my math check.
Its not a good simulation, but it is an acceptable abstraction.  The bonus to monster accuracy was a change that needed to be made (although I think they overdid it a little) because so many monsters were so weak.  

Is 10 a good starting point from a game-design perspective?  yeah, I would say so.  They are taking a binary hit/miss system and starting it off in the middle of the range (or close enough, really the middle would be 11, but who likes prime numbers?).  You get that slight 5% edge in favor of success, and then manipulate from there.  Sure, they could start at 15% success chance, but then there isn't much room for penalties and negative circumstancial conditions.  Similarly, if they started at 85% success rate, there isn't much room for improvement.  
All fair points, but how do you deal with some creatures needing bonuses to hit? For example, the orc gets a +5 to hit with their melee weapon. There seems to be no reason that the orc gets this bonus other than to fix an unbalance of power.

Thoughts? 



2 of it is the Orc's Strength modifier, all creatures add Str or Dex to melee attacks, so that would remain even if they lowered armor classes (another potential problem to consider). As for the other 3 points, that might be too high, I've long felt that many monsters have too much attack bonus. Since they don't tell us what the other 3 is, I can't say if it's fair or not, but I think that a low level monster like that shouldn't have more than a +1 weapon attack bonus, since a 15 is supposed to be a pretty good armor class in this game, but it often amounts to just negating the enemy attack bonus right now. It could be a holdover from the older packet where Fighter weapon attack bonuses started at +3.

@Keendk, you're right, I failed my math check.

I'll buy that two of the bonus comes from an orc's strength, but hobgoblins are weaker (11) strength and yet still have the +5 bonus to hit and no bonus to damage. It almost feels like they are bounding damage on these monsters rather than accuracy. IOW, they've made many of these creatures more accurate without explaining why. It's ultimately what got me thinking about reducing the base AC. It would alleviate the need for these kinds of bonuses.

 
Its not a good simulation, but it is an acceptable abstraction.  The bonus to monster accuracy was a change that needed to be made (although I think they overdid it a little) because so many monsters were so weak.  



I'm actually happy with acceptable abstractions. But it seems like the abstraction is broken if they have to give some creatures an unexplained bonus to attack. After all, aren't they suppose to be limiting the bonuses you get to hit? Why limit it in the players but not in the monsters?


One thing to keep in mind is that we don't actually have rules for creating monsters yet.  4e introduced the idea of asymetrical monster building where the monster just flat out did not follow the normal rules.  I would not be suprised if we aren't seeing something similar in play here as that was one of the great changes 4e brought.

The math on monsters does not need to make sense as long as it makes for a good monster.  It only needs to be reproducable so that DMs can create their own monsters and have some expectation of how challenging they are.

There could very be a general "Give monsters a +3 to their main attack if it is too low" rule. 
One thing to keep in mind is that we don't actually have rules for creating monsters yet.  4e introduced the idea of asymetrical monster building where the monster just flat out did not follow the normal rules.  I would not be suprised if we aren't seeing something similar in play here as that was one of the great changes 4e brought.

The math on monsters does not need to make sense as long as it makes for a good monster.  It only needs to be reproducable so that DMs can create their own monsters and have some expectation of how challenging they are.

There could very be a general "Give monsters a +3 to their main attack if it is too low" rule. 



Interesting and good to know. My last experience with D&D was 2e and I don't recall similar rules.