I got mine a week ago, and it took me ALOT of tries. I was at ilvl 493 when I did it, and the only reason I got through was Purification potion.
When I got him to 20%, Imps spawned and I thought I was done. Then I just kept Shadowburning him while keeping RoF up on Imps to have infinite Embers to SB and Ember Tap to heal the shit out of myself.
Was down to 18 HP at one point, so quite satisfied when he died
Most hectic sub 20% fight I've ever had.
Truly amazing fight, and I would LOVE to be able to fight him again.
They should make us able to queue for the Scenario all the time, once it's cleared imo.