I have seen alot of posts about this boss encounter in heroics and thought I would share an extremely easy way to do the fight. This fight is a tank check, everything lies in the tank doing their job correctly.
Let boss walk to far side of waterfall.
Pull boss through fire to get 1 stack of "buff", move him to the left side of lava falls. (If you use power auras, you can set up an aura to track this "buff", it makes it a ton easier Superheated Elementium Armor is the buff name)
When 5 seconds left on "buff" run through the lava falls to the other side , he walks through and stacks 1-2 more of "buff" but is out of lava falls.
Repeat and return to the left side, do this until ~ 10 stacks.
Let stacks drop and have DPS round up adds and kill them at stairs while you keep boss nearer to middle. ~ 44k HP and die pretty easily.
Move him back to left side and Repeat.
With 330 gear you will have to stack and kill adds 2 times if done correctly. With better gear once suffices.
This strat allows the buff to stack up slowly which gives a great deal of DPS time before you have to drop it. The lava puddles from the adds are a real pain so keeping them away from the boss is key. He should never leave the inner ring and the adds should be grabbed and killed outside of it.
You can give your healer time to catch up on AoE heals before you restart the buff stacking too. Use a CD anytime you near 50% health in the fight.
Hope this helps, I have taught my tanks to do it this way and its the easiest to manage with a newly geared heroic group.