I'm having good success with a Paladin, Warlock, Shaman, Mage, Priest team right now. I can't imagine dropping anyone at this point except *maybe* the Warlock - Shaman totems and backup heals pretty essential, and the mage puts out a crazy amount of DPS (and is simple to macro). Disc priest is enough to keep my group up with the shaman occasionally backup healing.

A lot of folks have success and love slaving Druids, but they strike me as more of a driving/active character given how versatile they are.