I have 3 shaman and 1 mage. The cast times are different so be aware of that. Its nice having frost nova and some aoe ability. The free biscuits are nice along with the portals. For two boxing I would suggest doing 2 of the same class. It will make all your macros much easier. Your not going to blow people out of the water like a 5 boxer. Having two that can heal or rez the other will be nice. If you have the hardware and can afford the accounts go 5 shaman.