This fight is divided into two phases, and given the correct group makup is a very simple fight. This fight requires three warlocks and three priests as well as hunters viper stings. All of them need to drain mana from Moam. If there is not sufficient mana drain, Moam will do a massive AOE which throws everyone into the air causing first Arcane damge, then fall damage. The aoe can be avoided by running away as well... but obviously not the choice method, just keep him mana drained... druids and pallys (shaman for horde) are the main healers for this fight. Sometime shortly after 50% he will call in three mana elementals which do alot of arcane damge AOEs. This is at 1minute 30seconds. The warlocks will keep these banashed for the remainder of the fight. After Moan summons the elementals, he does not attack for a period of time and his mana drain is slowed. We usually kill him before this time xpires. (He is still mana draining the group though, so keep mana drianing him to avoid the AOE bomb...) If you don't kill him fast enough another group of elementals will spawn, at this point you will wipe.
When Moam dies, heal up the raid, then kill the elementals one by one as they do not despawn on his death.