All priests and warlocks should still be mana burning Moam, but it will do an Arcane Explosion. Let it explode at about 80 seconds. Are you looking for cheap LastChaos Gold? This will cause Moam to turn to stone with very little mana, allowing warlocks and priests to keep up the mana drain so Moam will not not revert to normal prematurely. Everyone but the main tank and a healer needs to run away from Moam before it does the Arcane Explosion. A Greater Arcane Protection Potion on the tank, Buy LastChaos Gold is recommended. After Moam explodes, it is mana returns to 0. When it stoneforms, either kill or banish the Mana Fiends and finish Moam off.
After 90 seconds, 3 arcane elementals (Mana Fiends) will spawn - You want Moam to be below 45% by this time. Hunters can lay freeze traps in front of the Mana Fiends, then have a warlock banish when he is able. Using Feign Death/Freeze Trap, a hunter can pick up the add and prevent the arcane explosion. Warlocks will re-banish whenever capable. Another strategy requires a druid in healing/tank gear to heal ranged tank hard in phase 1, and then proceed to tank Ayamiss during phase 2, as Taunt doesn't work on him and Mocking Blow seems to be parried on every attempt.