I`d say it will work great. Even 2 paladins and 8 shamans. For cata... not sure, I think you`ll be missing out on a LOT dispelling then.

I was thinking of 10boxing using 5 shamans myself but then with a dk tank, pala tank,mage,holy pala and one more. So 2resto shamans and a holy paladin to pump tank heals. Tbh 2x ES is just to good imo.
Anyway for WOTLK content you`ll be set with that setup. Good thing is that you can offspec melee on shamans if you happen to need it.