Initial Impressions of dual Arenas after about 100 games.
My choices for 1st/2nd class. Anecdotal.
Paladin, Warlock, Shaman / Rogue, Warlock, Mage
Establishing early board is extremely important. In general, there seems to a be a lack of quality reactive offerings to make strong come backs with. What that means is, if you get ahead, you will likely STAY ahead and win.
The format (no buckets) rewards strong drafting knowledge. Without strong come from behind cards, having good drafting fundamentals goes a longer way. Curve and Tempo is king. Make sure you have proper "curve" minions (a 3 mana 2/2 is NOT a curve minion), a mix of initiative and some way to finish off games. There's no more predictive drafting, where we expect certain cards to pop up because the pools and buckets were so limited. Sometimes you just have to make Lemonade when you are offered lemons, this is the beauty of a system without buckets.
Defensive cards seem to be premium. Less taunts (Bone Wraith, War Bear, Kharut Defender) means less ways to prevent face damage. There also seems to be less good healing options as well (Voodoo Doctor, Farseer removed). A good sized taunt (even something as average as a 3/8 for 6 mana) is a nice luxury minion and usually is extremely hard to remove since the Meta is lacking removal cards in general. Bog Creeper and Tar Creeper feel ultra premium right now.
Removal is a premium. A deck full of good statted bodies is great, but you'll still need at least 1 or 2 strong removal cards to deal with trouble taunts, or to swing the game back while you are going 2nd. Take them early in your drafts to make sure you have it. In general, it feels like removal is more scarce, but i haven't dived too deep into the details just anecdotal. (I did get psy screamed 3 times yesterday on curve, DOOM'd, as well as Dragon Fired all in one day)
Take your time. Lots of cards we haven't seen for a while so don't make dumb misplays by not reading the cards. (I played Plague Scientist twice without the combo, and I played Doom Pact thinking it was Army of the Dead, all in 1 day) This also means to take some time to familiarize yourself with the card pools.
Don't play around anything - this is just my general feeling, but usual culprits like Scorcher on 5 or Flamestrike on 7 are not applicable here. Most decks are just so janky and fragile, you can't afford to play around anything most of the time and developing + face is generally correct.
Overall i'm enjoying it. It feels more like Arena (bad decks, limited synergies, rewards drafting and game play fundamentals like trading) Some negatives would probably include lack of class identity and neutralstone which favors the class with the better hero power. Another negative is the strength of going 1st. Without strong reactive cards, most deck archetypes will lean towards early tempo and aggression, this favors heavily the player going 1st. Its similar to the Rise of Mechs meta where early tempo was key.
Just some random thoughts so far, let me know if you agree or disagree, and your experiences.