It seems some are experiencing performance issues with the combat scanner. Currently it's always enabled, even in non-boss zones. So first step is to fix that.

Second, both the boss-is-now-in-combat and boss-died event handlers scan the combat log, so they will receive very many calls. An attempt should be made to ensure that no expensive calls are made in the event handlers, and if there are, look into if they can be cached, for example WBT.GetCurrentMapId().