I run druid tank along with 3x mages and a priest. Compared to the warrior the druid has far better threat both on AoE and single target, and the extra utility is nice as well. I just run in and spam Swipe and Holy Nova while the mages do their Flamestrike, Blast Wave, Arcane Explosion+ rotation. Much prefer it over running 4x mages and a priest because the tank gives me more survivability and allow me to pull more without risking mage deaths. On Alliance side I'd probably go with a paladin instead of a druid.