I distinctly remember them always taking my Spiritomb and then spamming her Double Team. Painful...at least, until I opted to always take the first Pokemon in the opponent's party so that my own lead (a Landorus-T) could Bulk Up again and again while Spiritomb used Double Team ad nauseam.
Black 2 FC: 4342-1045-6517 Trainer Name: Enigma http://i.imgur.com/6DdDc.gif
Does the AI favour ghost types or something? I remember when I was doing mix triples in the PWT a lot I only had 5 EV trained pokemon because I couldn't decide on a 6th, so I brought a Drifblim in (One of my HM users) as filler, and they always chose it. Made it hilariously easy when they sent it out on me.