I went with a Disc Priest, the team is still lower level.
I like that all five can mana drain, and I'll have access to Mass Dispel vs Bubbles.

If you want a mobile team (Affliction), you'll only really consider:
Disc Priest vs Resto Druid.

If your team will be Destruction (or possibly Demo), a plant yourself and DPS mode can work.
In which case, I'd look hard at a Shammy, mainly for Tremor & Bloodlust.