On my 1 shamy/4 pally team, I put cleanse (pally), purge (shammy) and spirit cleanse--whatever resto shammy decurse on on button. The pallies just cleanse whoever has aggro:
/cast [target=focus-target-target] Cleanse
The shammy will purge the enemy or de-curse a friendly.
/cast[target=focus-target, help] Spirit Cleanse
/cast [target=focus-target] Purge
It tries to decurse first if the main targets a friendly, purge the enemy (if the main has an emeny instead of friendly).
The rest of the pallies have it on round-robin, so one person isn't spamming it. One alt puts cleanse on the main first thing (incase main is feared). And then main has cleanse on himself after first push (since BGs and mobs get a lot of attention on one person, usually the main).
There are probably 120 ways to do it, just find one that works for you.