I still don't know if Ob Nixilis is better in aggro or control. But I do know it's not as good as people think in midrange. People are talking about sacrificing their turn 2 play like there's no cost to it but losing a 3/2 matters a lot. It's not like sacrificing Stitcher's Supplier or Eyetwitch, you're actually losing a real threat just for a 2nd Ob that might only make a 1/1 or deal 2/discard. That's not a good exchange unless your 2 drop made a treasure or killed something on death trigger.

If it was -1 to make a devil it would be amazing but being -2 makes it fair. If you -2 og and + the copy, og is on 1 loyalty so very pingable. Ob Nixilis alone can't win games unless you also have multiple threats / burn or if you keep the board clear with removal / sweepers. That's why I think it's best in aggro or control.

So my prediction is that people will initially try it in Rakdos midrange but it will underperform there. I think it will take time before people figure out the best home for Ob.

Hard to say how low it can go if it even drops in price. The problem is the card is obviously powerful and overhyped so even if it doesn't actually do anything it might retain a high price for a while.

All that to say I don't think there is an opportunity to spec. But I also wouldn't pay 30+$ for it unless you need to play with the card asap.