🚀 go-pugleaf

 From Wowhead:

For any healers trying to do this, you don't need to respec for it. In 
fact, I'd argue it's even easier to do as a healer than as a dps. How? 
Well, in the first phase, the thunder forge will throw out orbs that 
will give you the Overcharged buff, which mimics any healing you do as 
damage to the nearest target. The mechanics here make sure the Shado-pan 
assisting you will almost always have spare health to heal, so just let 
them take aggro, stand near a mob, and heal them.

In the second and third phases, the Celestial Defender has a buff on him 
that increases his damage in proportion to his remaining health. At 100% 
health, he gets a 300% damage buff (compared to what he does at zero 
health). As long as you keep him healed up, you'll have enough damage 
being done to get through. He isn't perfect at keeping aggro off of the 
Celestial Blacksmith, though, so you'll have to heal it as well. In the 
second phase, I recommend you don't use the anvils - they immediately 
reduce the Defender to half health (where he does half as much damage as 
he does at full health). Watch for the Lethargy debuff on the Defender, 
which decreases its damage, and dispel it whenever you see it up.

In the third phase, just keep the Defender healed up, kite the Sha 
during banish, and dispel any debuffs that are put on the Defender. One 
decreases its haste by 50%, and the other stuns it. Both are bad, but it 
shouldn't be hard to keep them dispelled. Overall, this phase tends to 
be easier than the second phase, though, as it's a lot less hectic. Just 
avoid the Sha's attacks and be ready to use an anvil during each casting 
of Insanity.