Finally pulled it off with a Purification Potion. 481 iLvl, mostly PvP gear. The last few wipes were mainly because no one told me there were only two Felhunter phases. I sent my Pit Lord away after the 3rd Imp phase thinking the Felhounds would spawn soon only to be swarmed by Imps, and by the time the Pit Lord got to the portal to breath them down, I was already dying.
It was an incredibly challenging fight, with me wiping for over three hours until I got the bastard down. Twice I wipe in execute phase for the reason listen above. I also took the advice I saw here before of not banishing or fearing the Doomguards and simply letting the Pit Lord tank them. Worked fine. By the time Kanrethad died my Pit Lord was well over 30% health without any use of Health Funnel.
Just remember so you don't fail like me that there aren't any further Felhound phases after the second one. After the second Doomguard is up, you will get consistant waves of Imps. Make use of them to collect Embers and Shadowburn that bastard down. After the 3rd Imp Phase, take advantage of the Charge debuff to Dark Soul + Shadowburn him, he'll go down in a jiffy no matter how bad your gear is.
Overall, I'm happy as all hell. I still think the fight should be toned down a bit, but it was nowhere near as hard as I initially thought it was. Just took loads of loads of practice. I wish those who haven't conquered this guy good luck in their future attempts, and remember, perseverance is the key!
P.S.: Motivational music helps. I was listening to Guile's Theme from Street Fighter when I got him down.