On Server #1502 PvE:
AI has been bugged on this server for a while. In general, mobs are neutral until you attack them. In some cases they will react, including with each other as they should, but most of the time they just sit there until you attack them.
Various bosses also have bugged AI, such as the Abyssal Remnant which just sits there and stares at you. This is obviously rather inconvenient, not to mention breaking the core game experience, because you can just walk around almost anywhere without being touched.