Ok, well, I run 5 Shammies at the moment. If I ever did move to 10 (and I don't think I ever will), I'd definitely include a water/food/taxi-boy, sometimes referred to as a Mage.

At 10, I would probably bite the bullet and include a Paladin tank and Priest healer as well.

So, I'd be 1 Paladin, 1 Priest, 1 Mage, 7 Shamans I guess.