This is an absurd challenge, insanely cheap and difficult.
What where your strats and preparation for this fight? I'm admittedly an LFR-baby, but no amount of ilvl increase would seem to have helped me here. mainly his crumbling arc seem to hit more than just the 180-degree "fire" that he prepares. I think I'm safe 5-10 yards away while being chased by his blood adds yet it still takes ~190k HP off me. I tried HB spam style to Unholy pew-pew with IT, DSiphon and DC, and failed.
Mainly because that crumbling arc likes to hit stuff it shouldn't hit. I don't know if I was lagging, or bugged, but it was frustrating nonetheless. Never had too much problems with similar attacks (like WoE's arcs)
Anyways, this is all academic and maybe a little rant-ish, because I just then changed Blood, no reforging with my full dps gear, and completed the tank challenge in 2 tries without researching (I failed the 1st attempt because I derped and watched Wrathion get pelted by DW's elementals when I was supposed to meat shield those). Tank challenge was insanely easy regardless, and felt kinda cheap, but I wonder if anyone else also took the same path.