UPDATE: There is a sweet BUG. If you reduce the cost of some 8 drop with Emperor Tharissan, (then it costs 7 mana) then it counts as a 7 and 8 in the questline so you're completing last stage with only one card. not anymore:)
Otherwise, this mini Galakrond package is nuts with the questline and i don't know why i didn't think about it earlier.
The deck is really fun, i've hit d5 with it yesterday but someone has to do something with that Darklare Warclock on steroids because the deck can beat actually everything except questlock. Wr is ~62%.
UPDATE: ok so basically you just can't win with Quest Warlock. And probably not only with this deck but every other control deck. They complete the quest on turn 4, they play Flesh Giants before turn 6. If you somehow handle those little minions and giants, you will die to Unlicensed Apothecary. Just hope for quick nerfs! Another very hard matchup is Quest Warrior but it's beatable. Hunter's is also hard but with Reno Jackson and some other healings you should be fine.
If there will be 10 upvotes i will add some guide.
The meta is still unstable but some conclusions could be drawn from that two days of playing.
Most of the time you win by surviving. Sometimes you win by Shadowspawn and rarely (because control is dead right now) you are able to win by finishing the quest. Don't even care about finishing it against any aggro or tempo.
Quest Warlock: as always, after expansion, wild breaks. For me it's even more frustrating than Stealer of Souls or Hysteria combo. I think the idea of the questline is fine, but it's just way to easy to complete if they can play reward on curve so just hope for quick nerfs. UPDATE: It IS possible. You just have to pull out Tamsin with Dirty Rat and then control the table (unless they get her back with Raise Dead ).
Quest Hunter: you need Reno Jackson very badly, and surprisingly, he doesn't give you enough heal so you have to have something else as well. From my experience the best way to deal with them is to survive until they play Tavish, then play your Illucia and simply empty their hand. It doesn't matter what you can give them, just do it and remove their spells.
Quest Warrior: he's probably almost as hard as Warlock but i belive, against warrior sometimes you actually have real chance to win. The problem is before expansion you could just win by surviving first 6 turns but now their first 6 turns are even more effective than earlier and the worst part is they don't lose tempo in the midgame. There is no other way except controlling the table as long as you can, and hope for a good draw and not Gorehowls form Juggernaut.
Quest Mage: it's usually just AMP mage but with something else. They have that spell damage +3, but they don't have that much spells on hand. Just try to make use of Rat and Mutanus.
Those decks were ones i've seen the most often. If you have a problem with deck i didn't mentioned, just ask me in comment, maybe i could help.
Honestly, this deck is very fun but on ranks from Bronze to Diamond 5, on D5-Legend, for now, you just can't be successful with any control (at least i wasn't) so just hit legend with some op quest deck while they are that good and enjoy this one when you're safe on legend, or just wait for meta to stabilize (or the balance patch).
Hope you'll enjoy it!