I've got a PVE group in my sig of Prot pally, Holy priest, Fire mage, Destro Warlock, Elemental Shammy. They are just as easy as 5 of the same class once you get the initial setup and configuring done.. I'm having a blast on them... and a bonus... when i did Princess in Maraudon.... i just changed macros on the holy priest to dps and the elemental shaman to heal for last fight.... since shes nature immune... worked like a charm and took like 1 minute to write the new macros....

So i would say go for it... and at the end.. you have a 70 of almost every class Ports/free food/summons/buffs. Its all good from there on out