Whether people like it or not, discard is one of the core themes of the warlock class. It's no different from getting more Beasts in Druid or more weapons in Warrior.
Also, Even warrior just got more support with Heavy Metal!. There are still many cards to come.
Edit: One of the main reasons people hate Discard Warlock is the rng aspect of the discards, which none of them include. Soulwarden also mitigates the rng already there.
3
Mad Max anyone?
2
Finally a real upside to Cryostasis . Too bad Freeze Shaman still can't work.
7
Treespeaker curves out nicely with Soul of the Forest. It's pretty common to hold back Soul of the Forest until you can build a big board to make it resilient to AOE, but maybe Treespeaker pushes that build to a more proactive usage of it.
3
I love the Krag'wa, the Frog battlecry, and Krag'wa, the Frog looks like a serious skill test. A lot of the the best spells you'll want to recoup will be overload cards, and in those cases you'll need to carefully budget your overloaded mana crystals (especially if you're using Electra Stormsurge or Zentimo). At the same time, Krag'wa represents pretty bad tempo for his cost, so you'll need to make sure playing him doesn't get you killed because your overloaded crystals will make it tough to play much more.
4
The Beast Within seems like a solid, Huntery card for anti-aggro/tempo swings. Pairs very well with cards like Cave Hydra or Stubborn Gastropod in any situation, or with Golakka Crawler or Hungry Crab in a pirate or murloc heavy meta respectively.
2
Mass Hysteria seems like a Priesty version of Brawl, so it's probably a pretty solid AOE. Not as good as Brawl, probably, but even if it sees no play this expansion, it will certainly fill a major AOE gap in Priest after rotations next year.
Not that Odd Priest is likely to be a thing, but because Mass Hysteria is a 5 cost card, it has some interesting implications for board clears with Glitter Moth in Odd Priest. First you buff the health of your minions to protect them, then you play Mass Hysteria to (hopefully) clean up the opposing board.
6
Spirit of the Rhino looks like a great, cheap way for Rush Warrior to get some major tempo swings. Good to see some real potential for an non-odd archetype in Warrior. But, since the spirit is itself odd, this might have some minor interesting implications for Odd Warrior with Dr. Boom, Mad Genius.
21
Zul'jin is a pretty interesting hero card. My first reaction was negative - Zul'jin comes down after Deathstalker Rexxar, but his hero power is a massive downgrade once you've cast the death knight hero. But later I thought better of that - Blizzard was never going to print a Hunter hero card with a hero power as broken as Build-A-Beast, the Zul'jin hero power is still an upgrade on the base Hunter hero power, and the effect is powerful enough to make you reconsider spells you might never have played before. (For example, Crushing Walls is kind of weak, but might be great cast alongside a Greater Emerald Spellstone and a full set of secrets in the late game.)
While Zul'jin seems to fit easily into Spell Hunter, I think that deck has too many poorly interacting spells today - your Unleash the Hounds can interfere with your spellstones and To My Side!, Kill Command and Hunter's Mark can backfire in a big way, Tracking can drive you into fatigue super fast, etc. Rather, I think that Zul'jin wants to be played in a deck with a focused set of spells that turn his effect into a kind of "late game refresh everything." If you run just secrets, the spellstones, and safe hard removal like Deadly Shot and Crushing Walls, Zul'jin will retake tempo on the board in a big way. Throw in a couple of Secret Plan's to generate more resources, and if you're playing a beast package, you can throw in Dire Frenzy, Master's Call, and even Flare to try and turn Zul'jin into a way to gain card advantage without digging yourself too deep into fatigue. Now you've got a card that clears the enemy board, fills your board, draws cards, generates cards for your hand, and shuffles cards into your deck - literally everything you could possibly want in a late game bomb. That's definitely a deck I'll want to experiment with.
4
Snapjaw Shellfighter is a cool card, if for no other reason than that it offers a crazy new tech card. I'm not sure exactly how it would be most effectively used - maybe you use it to "buff" a taunt or high value minion like a spirit card? It seems like a card that's a little weird, a little hard to find a home for, but something that's certainly worth a fair amount of exploration.
9
Sand Drudge can be compared to Violet Teacher, but despite the similar effect and statline vs vanilla, I think the applications are actually quite different. As many have pointed out, buffing a wide board isn't something Priest can really do, but getting a bunch of tiny taunts is a good way to protect minions like Radiant Elemental and Shadow Ascendant long enough to snowball their valuable persistent effects. And there are a few buffs like Extra Arms that might be useful if you can stick a Radiant Elemental on the board.
Regenerate might be really good, as it can pair with cards like Northshire Cleric, Auchenai Soulpriest, Lyra the Sunshard, and Wild Pyromancer, but you only have room for so many zero mana heal spells, and Circle of Healing will give it a serious run for its money. Even if it isn't that great, it gets 5/5 for flavor with the Troll theme of the expansion.