Some thoughts
Overall: Power level in general seems off the charts.
Quests are insane and don't seem incredibly difficult to complete.
Most games are going to be decided by who finishes their quest first. Hard to say if enough counters exist. The stream showcased every game finishing before turn 10... with trash-tier decks. Tons of taunts and Poisonous to hopefully delay games but will it be enough? Defense is rarely the correct play.
Druid
- Jade Cancer seems like it'll be at an all-time High. The Druid Quest should work with Jades.
- Barnabus+Kun Druid will be alive, OTK isn't dead.
- Tyrantus still trash compared to these other 2 more mature decks, but the idea of 0 mana Tyrantus and gain 13 or 27 armor same turn is appealing.
Hunter
- Aggro/Face is back, has multiple ways to prevent running out of steam, lots of deathrattles and beasts for stickyness
- I personally don't think Dinomancy will be good. Hunter power is too crucial to finishing out games.
- So many beasts, Jeweled Macaw is another RNG cancer card. Probably in every deck simply because it counts toward quest.
Mage
- Freeze Mage isn't dead, their Quest is the ultimate cheese. Giants on board+Alex, Charge Minions, or just Antonidas+Fireball chains, plenty of ways to kill off opponent once Quest completes.
- Burgly Bully is a great card for this Quest. I don't think Cabalist Tome is even necessary or ideal.
- Even Arcanologist adds to the Freeze Mage theme...
- I'm fairly certain that every mage deck will have a Quest package in it as a finisher. Lots of options on how to build, though.
Paladin
- Buff Paladin actually seems decent if not OP. Consistency is questionable but Paladin have plenty of tools to go into late game, and this expansion is giving them two 2-drops which are sorely needed for the class.
- Their weapon is expensive but seems good, but won't be in every deck obviously. Combos nicely with their legendary.
- Galvadon is just insane and seems like it'll be completed fairly quickly most games. Should count on him having Stealth & Windfury practically every game...
- Streetwise Investigator doesn't even seem like a good enough counter since it's 5 mana and likely won't have it and a removal in hand for the crystals you have available. Will need to use other methods: AoE Freeze, Devolve, Taunts, etc.
Priest
- Is 40 health enough for this meta?! Somehow I doubt it.
- Priest was looking strong but might end up being trash tier simply because they lack as much power as other heroes.
- You can try some janky divine spirit+inner fire stuff with the Legendary
- Priest seems weakest to me at first look
Rogue
- Losing Conceal and Pillager, makes Miracle a lot worse if not extinct.
- Vilespine Slayer seems like the winner here, going to be super annoying having this card continuously bounced & killing your shit over and over.
- Seems like you either go Quest Rogue or go home. Maybe Jades or Miracle will exist, but doubtful.
Shaman
- Losing a whole lot. Their early game isn't being replaced with anything as good as Trogg+TotemGolem.
- They do have some of the strongest counters for what is entering the game with Devolve / AoE / Hex.
- Aggro probably still exists, just slightly weaker early, but if they can get a turn 3 Unbound followed by turn 4 7/7 then have fun

Warlock
- I think Discardlock and/or Zoo will be super strong again. Everything they got helps them out here. Not much demon support this time around.
Warrior
- Control Warrior maybe back, but I have lots of doubts. They are losing Justicar and can't get infinite armor anymore.
- Sulfuras is nice.. I don't see games lasting long enough for it to matter. Too many tokens & sticky stuff out there to play around it.
- I really think Pirate Warrior is dead but maybe I'll be proven wrong. Too many taunts really screw up the deck already, plus extra weapon hate with Ooze, just seems bad.
- I think Warrior is going to be pretty weak, like tier 3 or 4.
Prediction Summary:
Tier 1:
Druid
Paladin
Hunter
Warlock
Tier 2:
Shaman
Mage
Tier 3/4:
Priest
Rogue
Warrior