Okay, you've sold me. I'd like to add ScarfTar to the threats list, for obvious reasons.
How is Jolteon a counter? It's weak in and of itself, and provided that this new pokemon outspeeds it, there's no way it survives a Shadow Ball or Psychic, even without a boost.
I'm going to start working on the possible teammates list for this poke. Just FYI. (Hint: MACHAMP)
EDIT: There are differences between this poke and Weavile. Jolteon is still a threat, as is ScarfGar. May I also add ANYTHING WITH A FIGHTING MOVE. There's the key difference: Ghost makes this thing far more useful than Weavile. Consider that anything without those counters will have a hell of a time killing this thing after it gets up a Nasty Plot. And trust me, many of those counters aren't common. Shadow Sneak? Sucker Punch? Pshaw.
That's my concern: it's far too overpowered after a Nasty Plot, and there aren't many priority moves to counter it: even if there are, they aren't nearly as commonly run as say, a Scizor BP countering DDtar, or a Vacuum Wave on an Infernape countering a Weavile, or a Ice Shard to counter Flygon/Dragonite.