Exactly. Multiple teams, mixed classes is the way I'm going.

Pally, Druid, Shammy, Hunter, Priest seems to be a good mix for me, as well as Warrior, Lock, Hunter, Druid, Shammy. Both teams cleared UK at 72 without problems.

Nice thing about mixed teams is that if one class get nerfed you don't have to scrap your whole team. Plus, WotLK is pushing us towards mixed classes to get multiple buff/debuff benefits.

My 2 cents.