So:

Protection Warrior - tank
Discipline Priest - tank healer
3x Arcane Mages - Ranged DPS

Hrm...

My tendency to go with the Holy Priest is because of their AoE heal ability since I'm still having a hard time with mob control with my teams. As I'm grabbing aggro with my tank, I tend to overlook the guy single trash mob that's been pounding on my caster for the last thirty seconds. AoE heals gives me the ability to splash healing all over when I screw up like that.

One of my favorite macros is "Heal The Guy Above You". Someone's being attacked that's not supposed to be? Quick! Everyone heal someone until I figure out what's going on!

Of course I could just get better at crowd control...