I setup my shaman just inside and to the right of the entry ramp. I group them up and have them all move together from keybinds. I keep them together and close to the entry ramp so the tank can pickup the adds in phase 2.

In phase one I keep the tank out in the center and try and avoid the pound. This is the easy phase go slow on dps if you need to catch up on healing from phase 2.

Phase 2 I run the tank to the shaman and drop consecrate then move over to the bottom of the ramp and wait on the elites. I focus entirely on the shamans in phase 2. When the ground starts shaking I run them forward a bit to miss the spike. If he spikes the shaman you lose all your totems. After the spike I back them up to the previous position. If non elites swarm them just magma. When the elites die take a deep breathe and get back to tanking the big guy.

Keep up the cleansing and nature resist try not to get pounded. This is a long fight, the achievement is to complete in less than 4 minutes. I solo healed a group yesterday with good dps and we didn't get the achievement.

If you have not so great gear you will run out of mana trying to heal through spikes.