I actually won outcotrolling him as Priest.
Insane game, wish I had it recorded. I played The Darkness early and tried to not kill the chests. Eventually I had to kill one. What I got was "draw a card, fill your hand with copies". What this got me was a hand full of that 7 mana Priest spellstone, that revives up to three minions after upgrades. With that, I could constatly compete with his board, but my spellstones got less and less and I still was fighting for boardcontrol without killing the chests, which took a lot of resources. Finally, The Darkness awakes. Boom, Lightbomb. Well, shit. However - I had the dungeon run power that activates my battlecries twice - so there were another 3 candles in his deck. Last spellstone resummons a dormant The Darkness. I finally draw my deathknight and Raza, now being able to compete with his board. Still running out of steam, hard fight till the last turns.
No candles to be seen. He draws and draws, no candle. I actually started to think, maybe this is bugged and once The Darkness awakes, it removes all candles. But no. Literally the last 3 cards in his deck were the additional 3 candles - this might be insane RNG, or still is bugged. Anyway, this wakes up The Darkness. Vustrasz already in fatigue for a few turns, no removal for my huge threat. My last card drawn is the treasure that adapts a minion once for every beaten boss. Adapt The Darkess, above 30 attack windfury to finish him off.
Hell, that was satisfying :D