I tanked all the heroics (cata beta) as a warrior and I know you can get alot of vengeance with a big pack of mobs. I would usually be top dps in packs of 5 or more. And the 17 sec cooldown on shockwave comes around pretty fast, and you can add damage to it from the thunderclap talent.
Even if someone didn't assist, taunt is easy enough. The key is to shockwave and spam revenge/cleave. Do a short leap if needed. And if its still too messy you challenge shout. You'll have enough vengeance from that to hold anything if it lasts.
Its prob easier to tank on a paladin, but they don't have the stuns. Warrior is a stun machine.