I wouldn't say that Bat Rider is OP, he is only good for targeting 1 enemy at a time. He can do some pretty decent AOE damage in teamfights, but thats only where he shines. He can easily be killed 1v1 by most heroes, get a disable and he is pretty much dead. If he gets the correct items he can be dangerous in the aspect that he can drag one of your teammates out of the safe zone.