Do a mixed group, for the love of everything, mixed group. Throw in a mage for int, food, ports, Priest for Fort / SPI / Shadow prot / Fear ward, Shaman for totems maybe, Warlock for healthstones / soulstones, Hunter for strong DPS.

You can also do things like Frost mage, Destro lock, Shadow priest, and or Surv Hunter for Replenishment procs. Also make sure if you run alliance, to get at least 1 dranei for the 1% hit, it makes a difference when you want to start heroics and your hit rating sucks, shadow priest will also help with this.