This list was difficult to make. Descent of Dragons is one of the most insanely powerful Hearthstone expansions ever printed, and takes me back to the days of Kobolds and Catacombs; in a good way.
Some criteria real quick. I’m listing no Commons on this list; Common cards are very cheap to craft, and you’ll be drowning in duplicates of them by the end of the first month of the set even as a free to play player. I’m also disqualifying cards that I feel will require a lot of support from other expensive cards to be good, which leaves out cards like Ancharrr, which I expect to be the cornerstone of a new Pirate Warrior. These cards do not necessarily deck defining (though some are), but all are great cards on their own merits, which can slot into at least one type of deck I expect will be standard.
Druid: Breath of Dreams
Two mana, draw a card and gain an empty mana crystal. That text is bonkers persuasive to anyone who’s been playing Hearthstone for a while. That is original recipe Wild Growth, was the developers nerfed from three. It also draws you a card, with the minor drawback of needing to run a few dragons in your deck.
Hunter typically runs Eaglehorn Bow and the Secret package in several decks, be they Midrange or Aggro, or beast themed or otherwise. Stormhammer is comparable to Eaglehorn Bow. Both are three mana three out of two weapons which “gain charges” if you do something, but keys off dragons rather than Secrets.
Hunter has a lot of dragon support already (not many people remember that Witchwood had a Dragon Hunter pre-built), so this should be very easy to use the card.
Mage: Elemental Allies
One mana, draw three cards. All you have to do is play elementals two turns in a row. Easy to complete with an insane reward. It reminds me of Aluneth, but you can control it when it goes off.
I had a few options I thought about putting here, like Sky Claw, but eventually went with Sanctuary. A 3/6 with Taunt on turn three is good, and even better on turn two if you Coin it out. The activation requirement is pretty straightforward that early in the game, and will rise exponentially if this ends up being a slower meta, which I imagine it might be (a lot of the cards here push Midrange and Control decks).
Priest: Fate Weaver
It has a pleasant vanilla statline, and it reduces the cost of cards in your hand by 1. The only stipulation is that you need to be running Galakrond, but I think it’s going to be a solid deck, if not top tier. Either it will be a hardcore Control deck or somebody will come up with some wonky combo Priest that uses the Galakrond package just for this. Either way, it should be good.
Rogue: Necrium Apothecary
I almost put Waxadred in this spot, until I remembered this card could potentially draw your Waxadred and also give you a second copy of it, mana sooner. Plus, it’s merely a more versatile card and maybe a good tempo play in a different deck that happens to run some good Deathrattles rather than a whole Deathrattle Control Rogue.
Shaman: Dragon’s Pack
This card is a five mana 10/12 taunt, essentially. Even better since it’s broken across two bodies, making it harder to remove. That’s just good value, and a pretty clear pick for a more Control oriented Galakrond Shaman. I was a hair’s breadth away from putting Cumulo-Maximus here, which may end up being the better option (Overload Shaman and Quest Shaman still look like they’re going to be powerful decks). Again, I believe in Feral Spirit+. The original got me through some rough times when I was starting.
Warlock: Veiled Worshiper
Four mana 5/4 is already a decent stat line, but drawing a whopping three cards with it is kind of insane. This card is a considerable push toward playing a Galakrond augmented Zoolock deck, which looks like it’s going to be very fun.
Warrior: Scion of Ruin
Warrior, as usual, gets a lot of good cards this expansion, but four mana for 9/6 worth of stats with Rush is perfect in both more aggressive and more Control oriented Warrior decks.
Neutral: Dragonmaw Poacher
This card is the “meta breaker” card, and everyone should own a copy of it. If dragon decks are powerful, this is powerful, and they are guaranteed to be active, at least for this expansion. Dragonmaw Poacher exists to make your opponent afraid to play dragon cards in the early game, and is still good late game; there are very few scenarios where an 8/8 with Rush for four mana is terrible.