I first noticed this bug on a dual 4x defender or guard, it's the same bug that also make rumir class unplayable. the more you atk something, the more you lag and can't click skills etc. this target died at 6:04 in the video yet I kept hitting it for another minute and 20 seconds ............ fix it it makes the class not playable.
https://youtu.be/aoYzgYpWpk8