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You could also play a half-elf ranger hybrid seeker MC skald. Take Rapid Shot via archery master feat and any of the skald at will aura powers. The skald at-will powers last until the end of the encounter, if you don't use another one.

This turns your seeker ranged basic powers into area burst 1 and you get to buff your whole party with it. You can even use seeker ranged basic encounter powers in between. You don't even need high DEX for this build, because your ranged basic attack is WIS based. Ranger has enough powers, like "Fox's cunning", with a cool effect that don't require DEX to attack.

For example, if your at-will power is Biting Swarm and you take Words of Gravity from skald, your enemy has effectively -4 to hit. Or use Grappling Spirits as your at-will and the feat World Serpent's Grasp, to prone on every second hit.

Seeker and a "rebounding weapon" both have encounter powers like "miss: make a ranged basic attack", to add even more fun to the mix. These are both very good options to lose your seeker ranged basic encounter powers (like Winter Spirit on LV 3), because they don't take the -2 hit penalty from rapid shot.

You should use a superior crossbow instead of bows as your weapon, to make up for the accuracy loss of rapid shot. "Crossbow expertise" also lets you ignore any form of cover. Only concealment is a problem, because there's no way you can completely ignore it. A "homing weapon" lets you ignore normal concealment, at least if you prefer accuracy over a rebounding weapon.

For constant CA, take the fey beast tamer theme.

A note about rapid shot. It targets creatures, you must attack allies, too. But each attack from rapid shot is an independant attack, so you can use a normal ranged basic attack instead of your seeker at-will power with a different weapon against your allies. So your best bet against allies are improvised ranged basic attacks with low DEX or heavy thrown weapons, if you have like STR 8. You could even close your eyes, so your allies have total concealment. You DM may find this to cheesy, so i would rather not use this tactic.

If you don't care much for "control", subsitute hybrid seeker for executioner. You'll lose the cool ranged basic powers, but you can add 1D8 extra damage to one of your attacks each turn and do more damage with assassin's strike. I never tried this build, so i can't give you many tips on it, but it should also work.