Everything will work. A very nice combination for me is:

- pally tank
- shaman dps
- shaman dps
- warlock dps
- druid healer

And recently i've discovered the joy to swap chars back and forth, depending on the mood of the day and the encounter.

- 5x shammies for pvp rocks. Even running 5x shamy through some dungeons is very fun.
- having another tank to lead with makes it more interesting (druid or dk)
- having pally tank + 3 dk's + disc priest is fun as hell