CC shouldn't really be an issue. If it's a tricky pull of 3+, either have coth ready, or kill off the puller and rez
Strong class choices you have there, and I wouldn't change them. Shammys provide a boost to melee classes, which includes pets. If you sub in a wiz for the mage, you will loose not only a panther target, but also all the pet toys on tap which the mage will provide to the 3 pets.
As for who handles which account, remember that mages can also be considered low maintenance: /pet attack, /cast rain, /cast nuke. Sure, with any character, the more time you spend on them, the more dps you will crank out, but mages can do quite decently between a few alt-tabs. The one who will be busiest would be the shammy, as if you want to maintain panther and dots, you will be casting almost non-stop...
I suppose if you want to crank sk dps as well, he will be casting.
But anyway, sounds like a fun combo. GL with it
Muk