Yes Erebus with bats is pretty brutal on Crucible. I have a build for him that relies on minions, mist and bats to do just that. It requires high mana regen but once you have it you bat over the gap, walk in front of the portal, DONT TAKE THE FLAG, and turn into mist. Enemies will come out of the portal, die in your mist and become nightwalkers. This is INCREDIBLY frustrating for your oponents as, if you can stay in mist long enough, there is nothing they can do about it. Once they realise this and leave, you unmist to regen mana and take the portal. When they realise youve done this, they will come back. Turn into mist and let them take the portal. Their wave starts coming out again, dying in your mist and becoming deathwalkers. Rince and repeat.
It is a VERY effective tactic for Crucible and Ive had other players calling me all kinds of names for using it as well as blaring that Im a cheater. Works very well, but doesnt make you any friends.