Hello! I also got my green fire couple days ago with ilvl 485, without use of any potions / flasks or what so ever.
Strategy: Burn him like a mofo, use charges until the first imp phase to stop him casting the curse on you and take gateway on CD to keep yourself as low on aggro table as possible.
I actualy stunned the first hound to give my pitlord more time to get out of line of sight from the hounds, popped CD:s, killed 'em all with little trouble, although i didnt get much time to actualy do dmg to boss on this phase.
Re-enslave the pitlord during summoning of doom lord, charge to boss for extra dmg, use pitlord heal on you and take GW to drop agro.
Then it's practicaly repetition while also keeping a Doom Lord banished (i put him on my focus and focus banished when needed) and for the last minute, you also have one Doom Lord that has to be kept feared.
Finished the boss easily on 3rd imp phase when he had already went sub 20% by throwing RoF on imps, popping all CD's (defensive and offensive), charged the boss and burned him to oblivion.