This was incredibly difficult. I kept failing and failing, coming in with slightly better gear, failing, gearing up more, failing etc. i'd guess this was my 12th attempt or so, and i made it to part 3 maybe 6 times.
strategy i used was pretty straightforward, just tanked everything in the quest at once and healed through it. i didn't max my concentration score so part 2 was pretty tough, but eventually i found a hat with +15 concentration on the auction house and that was good enough (to cast fireshield scrolls). i picked up the remove curse spell for part 3, and i have to admit i was skeptical at first but its a lot better than potions.
the death was in part 3, when horoth was at about 25%, pretty much the same hp he had every single time i failed part 3, but i used my extra life to good effect and recovered.