it's going to be hard to beat the pally + 4 shaman. they are so simple and so easy to play. huge passive healing ( 4x healing streams) , huge passive AoE ( pally consecrate, shaman magmas ) tremor totems, earthbind totems.

I've tried mixed teams like mage, warlock, ret pally, prot pally, shaman healer and I really had a rough time of it. rough compared to the pally/shaman team. Someone is almost always dead and it's usually the ret pally stealing aggro. I still play my off teams but I just don't like them as much as I like my main team.