Make your bots team friendly and use the followplayer output event. They'll veer away from you to kill zombies, but they'll come straight back once you get far enough or if they kill the threat facing them. Now, unfortunately, you're going to realize that friendly-bot fire is going to ruin everything. For that, i'm sorry. I have no solution for that. You'd think it be more wide-spread, but people don't use bots as much as they should I think. You could use slayer to disable friendly fire with bots, but you can't really uh..."event" them. They will still attack hole-zombies, but you can't get them to follow you. Idk. I'm just starting out with slayer. Maybe you can, but I don't know how. Anyway, that's how you can get a bot to help you kill zombies. Make sure to use the power-on, power-off event to give yourself some space, as they will often block your way. And yes, as that other guy said, they will attack hole-zombies automatically, as well as any team of regular hole-bots you "event" to oppose you.
Does this uh...does this help at all? ( :)