"Other than being a completely different Pokemon altogether... Nasty Plot + 100 base speed + Stab Fire is certainly not useless."
Oh, I agree, and I may even try it. However, with how common Groudon and Kyogre are in Ubers, Ninetales' defense means it has difficulty finding a chance to set up; if it fails to KO either, it's gonna get smacked with an EQ (which Groudon can come in on freely), Surf, or Water Spout, and die.