Okay for those of you that have beat the boss:
When he gets below 25-20% hp do all the lava grates become active for you with 1second in between each reapplication and do the static balls come out faster and full blown?
theres this stuff called solid floor, i hear all toons have Cds that increase dps/healing.
take him back to the middle and just nail him or drag him to an edge. if you have sage healer stack up and aoe heal it basicly negates the fire, if your dps is bad just kite away from balls just like rest of fight, it will die
pro tip for last boss dont stand in front of it is genade move hurts. more than any op boss on NM apart from probs fabrictor fire :P