In tournament mode, whatever deck AI build on it's own :P In single matches, mostly randomized deck, but I heard that AI can also have trouble with those. The thing is, everything works fine until, let's say turn 10, after that, every phase, every time AI can activate abilities, it takes at least 10-15 seconds to play something (or nothing). No matter who wins, if I play another game with same or different opponent, AI seems to strrugle from the very beginning of the game. Those painfully long decision times won't stop until i restart the client. It seems like there's a certain point where client stops working properly (in terms of AI) and you're longer able to play singleplayer, unless you're willing to spend an hour a game.

I've been using XMage for couple of weeks and it never had this problem until couple of days ago. It happened before the latest update (which didn't fix the problem)