Uncrackable is so underrated. I've had it used against me on turn 9, just so that they will survive until turn 10 to play Wall Nut Bowling or Cornucopia. And they (usually) win. I see people all the time saying it's a "death stall' card, but it's more than that. For example, imagine you are low on health, and they have the clear board advantage. Well, just play Uncrackable so you won't die, then play Magnifying Grass to kill them without worry.
As for Devour, it's a great card, but "A+" is a bit too high IMO, because low health minions are everywhere in the current game meta. Fishy Imp, Tennis Champ, ect.
That's just my opinion.