Arena guesstimates:

Dark Iron Skulker - Top Tier pick. It's basically a (slightly gimped) consecrate, plus a 4/3 for 1 extra mana. Can't see picking much of anything over that.

Grim Patron - Terrible in Arena; the gimmick is going to be far too unreliable to activate and the stats are bad. Could see decks being built around it in constructed, but it's Silverback Patriach level bad in Arena.

Blackwing Technician - Average in Arena. 2/4 for 3 is not great, but it's not awful either. If you've managed to pick up any Faerie Dragons (which you almost always choose in arena if they're an option, and which should get even better with the expansion), it's potentially a Taz'Dingo for 3, which is through the roof.

Hungry Dragon - This is the hardest one to evaluate. I'm going to say this will probably be a very good arena pick because the stats are obviously nuts. But the drawback has the potential to bone you in some cases -- it's a bit Deathlord-ish, in that respect, although certainly less likely to outright lose you the game than Deathlord. The stats make this card hard enough to deal with that it's probably going to be at the tippy-top of most arena players' tier lists until they have a chance to play with it, though, regardless of whether it turns out to be a super-yeti or a less-bad Deathlord.

Rend Blackhand - Bad in Arena, although both the downside and the upside are less severe there than in Constructed -- very few BGHs, but also no way to guarantee a Dragon in hand. Better than Milhouse and Cho, but worse than probably 75% of Legendaries. (For the record, this card also gets my Dr. Boom Sleeper Pick for BRM Constructed -- I see a lot of people saying "It's not that good", and maybe they're right, but my left-field guess is that this is a card that a lot of people wind up running, possibly in combination with either Onyxia or Faerie Dragons (depends on further dragon synergies in the set).)