Well i just finished Heroic Trial of the Champions with 2 Healer Setups and farming epics is now my daily task.

1. Team
Pally-Tank, 2 Elemental-Shaman, 1 Resto-Shaman, 1 Boomkin

just setup one Button for chainheal and have your toons on follow. setup 3 tremor totems. i usually don't need to purge the healing of the shadow mob, but should give it a try - might be easier.

2. Team
Pally-Tank, 2 Elemental-Shaman, 1 Diszi-Priest, 1 Boomkin
This battle is more challenging. setup 2 tremor totems, setup prayer of healing and chainheal on the same button. on this fight i use to cast my Bloodlust

i still wipe sometimes on my second team, but 3 shamans casting chainheal gibes you enough time. purging might be very helpful, i'll give it a try