I was thinking about this idea a while ago.. but what it ends up doing is just giving him 3 skills. Maybe If there were 3 (or more) types of cards that you could get, but what type CM picked was random, or very difficult to choose. They could have effects like, Blue card: higher damage, Red card: AOE slow, Gold Card: single target stun. And theres lots of other things you could think of as well. maybe a healing reduction card, or a poison card.
So the cards could be slightly better than your average skill, but you don't know what one you're going to get.
Or you could leave the 3 card types unbalanced and just make the better ones rarer.