I tried 5 shammies. Yeah, it's neat with all the possibilities with chain lightning, totem stacking, heals, etc. I got bored with it fast though, maybe because I played a shaman for 2 years.

4 locks + priest, I'm interested to see how that group fares in lvl 70 instances.

I opted for a pally, warlock, priest, and 2 mages setup. Lot more of a hassle to set up, but I think it'll be worth it in the end. If I decide to swap classes, I have plenty of toons I can transfer and put into the mix later on.