When he's near half health, lure him as far away form the lava as you can. :P keep pray up, ovl, chaotic maul, and basic abilities. Kill the ranger that spawns in the beginning and ignore everything e
use more than just the [kick] / [backhand] ability that stuns, and you can pretty much stun lock him into not healing at all. the main problem i had with the boss was not watching my prayer.
