N’zoth for neutrals.
I think it really depends. It seems like all legendaries are useful in their niche. Even Nzoth is only good in DR control decks (obviously), and there aren’t that many viable DR decks right now. Rogue is one (but I expect it to die actually, Rogue just can’t play control. Maybe when they add healing), Priest and Paladin are 2 others that seem viable right now, but I doubt that Priest will last long - Priest doesn’t have that many good DR minions since Dark Cultist left. The neutral DR minions are actually pretty bad, save for Sylv and Cairne. The one standout class minion is of course Tirion, and Paladin can actually play control, which leads me to believe the Nzoth deck will be Paladin. It’s basically a heavier Anyfin deck.
The only “must craft” legendary seems to me to be Twins, but obviously only if you want to play a Cthun deck.
So I would say, there aren’t any “must crafts” at this point. Most legendaries are “craftable” and could be well used in their niche, but there are no Dr.7s at this point.
I’m not sure any of them are good enough to warrant must-haves, but I’d second N’Zoth as the best of the lot, as well as the one that’s seeing the most play competitively.
I’m sitting on a bunch of dust, too – waiting to see how things shake out. Looks like I might be using some to fill in the blanks in my Classic set – maybe Cairne and Black Knight – but I’m gonna wait a while to see if their comeback lasts.
Black Knight might do really well given the rise of the Cthun Druid. Cairne is also better compared with the current power level - it’s really rare to get sticky minions now, double Yeti has never been better.
I crafted a Cairne myself for Nzoth Rogue and Nzoth Priest. I don’t actually think these decks will be top tier though. But Cairne is pretty much required for DR decks now given the crappiness of current DR minions.
I played Kripp in the arena today. I doubted it was really him but I checked Twitch and sure enough there I was with over 30 thousand people watching me play. It wasn’t much of a game unfortunately. I had a ridiculous shaman overload opening into a turn 6 win. Nothing he could have done about it I don’t think. I watched his stream after the win and he was so salty about it as expected.
Give us a link to the VOD?
Oh yeah, I didn’t think to check that to see what he said during my game. The game starts 2 hours and 32 minutes in. I was playing slowly because I wanted to cherish my time with Kripp and take some screenshots 
Everything old is new again. Tempo Rogue, the very first Rogue deck that I truly loved, is back in business. Winstreaking my way up the ranks now, turns out, with Zombie Chow and Haunted Creeper out of the picture, Coin + This is our town, scrub. Yeah beat it! is still the most OP opener in Hearthstone.
Dark Iron Skulker, Undercity Huckster, Tomb Pillager, all marvellous additions to tempo Rogue.
I wonder how many people have never had scrubs played against them before? There must be many - it’s been years since I non-ironically put them in a deck.
For anyone that wants to try a straightforward, simple but effective deck that isn’t face:
What’s the best class for a c’thun deck? Control warrior?
Is control priest viable? I haven’t really looked at the C’thun cards, but I like control priest out of all the control decks. Except for maybe Reno freeze mage.
A mage just used his C’thun to clear my board and take me down to 1 hp. He has 4 hp. Little does he know I’m goofing around with a Reno Hunter deck. I only had the one card, too. Has to be one of the most unexpected Renos ever.
Druid seems to be the best now. Warrior is also viable, but it’s more of a control warrior with alternative win condition I think.
Hilarious brawl. Found some rock-paper-scissors (though there may be additional possibilities)
Doomsayer/Darkbomb Warlock beats
Mechwarper/Metaltooth Leaper Hunter beats
Astral Connection/Deathwing Druid beats the doomsayer deck.
I also saw a Mechwarper/Gorillabot deck, which seemed good, and a Timber Wolf/Webspinner deck, which seemed weaker than the mechwarper option.
Mechwarper/Iron Sensei worked to get my pack, which contained Millhouse Manastorm!
I think I’m done with Brawl for the week though.
I played Target Dummy and Bolster. Most games they conceded by turn 3 or 4, lots gave up on turn 2 looking at three or four 2/4 taunts.
Rarely lost a game, mainly those where I didn’t have any Target Dummies on the first two turns. Shamelessly played on to gain 100 gold to buy another pack – got a Golden Hogger (the new one, whatever he’s called.)
Innervate and fatties. Ancient of Lore at first, then Ancient of War as games seemed to be decided faster than I had thought. I played against Evolve and the new Murloc that spawns an Ooze. That was impossible to deal with using just Ancient of Lore.
Won with Mechwarper + Metaltooth Leaper.
I first tried with Flame Leviathan + Ice Block. Didn’t work. Was funny, though!
Maybe I should try again but with Flame Leviathan + Frost Nova.
EDIT: Yup, Flame Leviathan + Frost Nova works. I knew I should have kept him!
I also got there with the zero drop murloc and the one-drop murloc lord (forget what they’re called).
This brawl is so silly and has so much potential to be fun, but it’s just going to be an army of hunters with mechwarpers and metaltooth leapers. WOW I’M SO AWESOME, I CAN WIN 100 GAMES WITH THE SAME COMBO. YAY ME.
Innervate + Coldlight Oracle has seen more success than failure so far. Play Innervate to pay for Coldlight Oracle, play Coldlight Oracle to draw more Innervates and Coldlight Oracles, 20 GOTO 10. It loses to Ice Block + Fireball because it can’t bring them down to fatigue if no murlocs die, but against anything that even tries to contest the board, you can quickly get the opponent down to ~15 life to your 30 then fatigue them the rest of the way.