Hire a few expert botters, if necessary as independent contractors, who are in the know on the forums, tools, tricks and what not and then put in place auto-ban detection systems with some anti-cheat software. Those "now white hats" can remain "undercover" and in the cheating/botting community to help keep up with the adaption over time.

Also get more GMs and/or recruit some customer relations folk in game that can issue bans.