the only time i wish i had more than my 3 shamans is for pvp. for heroics and other 5mans, i team up with my prot pally/destro lock friend who fills int he two spots. he worries about tanking and i pew pew and heal with my 1 guy i respec resto. if u got a friend who is commited to this sort of setup, why not do 3 at a time. i got lucky