I think OWK needs additional debuffs available to his Mind Tricks, or maybe an additional special. Right now he can Ability Block for 1 turn and Offense Down for 2 turns, with a 65% chance to remove 60% TM. That's a good start. Now if he could also apply, say, Defense Down for 1 turn and 25% Speed Down for 2 turns. Applying all at once is too much, so give him another special Mind Tricks 2. This way he could keep stacking debuffs on the enemy in consecutive turns. If you ignore him, you'll find yourself with Offense Down, Defense Down, and Speed Down.
Either that, or reduce his cooldown to 3 or 4 turns. You've got to give the opposition a reason to need him gone. Of course, then they have to deal with his departing buffs, but Asajj could just wipe those right off the board.
Right now, there's just no reason to attack him early. He's slightly annoying, but can be mostly ignored until last.