I was thinking about running the Nasty Plot set while hiding behind Gengar. The most common attacks to a Gengar are Psychic, Dark, and Ghost. Zoroark resists 2 and is immune to one. No idiot would explode on a Gengar, so he's safe from exploding leads too. Also, his two weaknesses, Bug and Fighting, deal 0.25 and 0 times damage to Gengar, so he'd be pretty well covered....
I had exactly the same idea xD
It didn't work out too well though, but maybe because I was just stupid and put a choice specs on it... I wanted to have enough power so that he can really KO the surprised Pokes, but it was a dumb idea, because the enemy will of course switch to something that won't get too much damage from your attacks.
(I didn't use nasty plot because Zoroark isn't safe from scarfers and priority users, there's so many of them ~_~)
Another thing that helps him is Gengar and Zoroark both use Focus Blast. Too bad it always misses though lol.