Well, I'm about to hit 60 on the toons to fill out my 10-box group (thank you RAF!), I expect hitting L70 will take maybe a month if I push so... as it stands I'm planning to gear up a little bit and hit Kara before WotLK.

I ended up going with 2 paladins, 8 shaman, a druid, and a priest. Yes, that's 12 characters - as I advance in gear and need less offtank/heals then I can swap in more DPS.

1 Protection Paladin (tank)
1 Prot/Holy Paladin (offtank/offheals)
1 Holy priest or 1 resto shaman (main healer)
1 Boomkin, who will also get all feral and healing leather if the resto shaman doesn't need.
7 or 8 Elemental Shaman.

So I have a bit of flexibility there, I can run with 1 to 3 tanks, 1 to 3 healers of various classes, and the rest DPS. I think it should be capable of handling any 10 man, as long as I can control them well enough. It will be an interesting challenge for sure!
Well, I guess if they put in Nature immune mobs then I'll be stuck... just have to level up Warlocks or something I guess!