My 2c...

Spec the pally holy and heal with him, dps with the shamans.

I go in blasting with chain lightning whenever I can, EM as available and lots of LB spam with assorted earth shocks when it's off cooldown. Agro rotates between the shamans on trash, the ONLY ones that are dangerous are the destroyers (big 2h axes of pain) and I normally can have one dead and the other softened by the time they reach me... I pull with LB, CL, LB, and then they are in melee so I earth shock... that almost always kills the one, switch to the 2nd and CL, even if the 1st isn't dead I switch since the chain will kill him for sure...

Grounding Totems are godlike for trash pulls with casters, bosses are easy except the 3rd, which I try each time, but never mroe than once.