I have two buttons, one for all out DPS and another for some percentage of my guys to become healers.
if the instance is going easy I only have one healer, if it's getting hard, I conver two to heals.
example:
button 2 = 4x LB
button 3 = 3x LB and 1x Healing wave

example: for harder instance
button 2 = LB on all 4 shams,
button 3 = 2x LB, 1x Healing wave, 1x chain heal

i use focus method of control so I have something like this on the healer button, this allows my healer to heal my stone or fire elementals as well as my pally depending on who has aggro
/cast [target=focus-target-target,noharm,exists] healing wave; [target=party1] chain heal