Here are my bets. This is just my opinion obviously:
1. Death Knight: loses absolutely nothing and it is already one of the strongest contenders in a heavily powercrept meta. On top of that, it is getting really strong support. Death growl scares me.
2. Demon Hunter: the rush tokens + Halveria package looks crazy. Might end up being crushed if it is denied the board presence necessary to go face tho; so maybe it doesn’t live up to the hype.
3. Warlock: more implock. Seems pretty robust, but I’m not sure the fatigue package makes up for its weakness against control decks. I am not sure Symphony of Sins goes in the deck but that could be the ultimate control punisher it needs.
4. Paladin: I don’t rank it among the top simply because it can be easily controlled with removals. I predict this is going to slap your face and roll over your dead body even before it gets to play Countess if you can’t deal with its divine shielded early minions.
5. Shaman: there isn’t a lot of hope for shammies this expansion but I feel it will be stronger than predicted. It can also rely on a few different archetypes (totems, murlocs, overload, evolve, deathrattle or any combination of these), so I think there is a decent chance it will find a winning strategy.
6. Hunter: I don’t think there’s a whole lot to be super excited about here but I think the beasts package will have a decent performance and will at least see a similar amount of play as good-ol beast hunter is seeing right now. Not the best, but playable.
7. Druid: I must say, at first glance I thought druid was going to suck really hard this expansion. I thought the legendary minion was a lot worse than it actually seems to be. I think druid will be decent, but not amazing. The legendary spell is terrible tho.
8. Mage: This is the class I feel less confident ranking. If the whole lightshow stuff does work reliably it could be pretty strong, but I haven’t really seen that happening. There could also be an aggro mage deck that hits the jackpot, but with so many aggro decks already looking promising I am not sure this can do this job better than the others
9. Rogue: I have discussed rogue extensively already so I won’t repeat myself. I think the new cards look flimsy at best. Rogue will be as good as miracle rogue turns out to be. It might look like miracle isn’t losing much, but without Drakka (no more mailbox dancer and incompatible with record scratcher) I don’t think it is going to be anywhere near what it has been during MotLK. There could be a pirate rogue lurking the shadows that no one is seeing coming.
10. Priest: yep, doesn’t look amazing. Not much else to say here. It has some interesting pieces tho so I do think there’s some hope in the horizon. But for now it just doesn’t look very strong.
11. Warrior: wait… Warrior? Is that a new class? Seriously tho, I think a list with BRnR could work out and be decent. I will be trying my best to make some warrior list work. It just doesn’t look great.