I think since the update the update cycle for enmity seems to has been adjusted. So when a tank looses hate anytime during a server check the mob will always turn no delay, so maybe an adjustment to priorty between finishing current qued actions compared to enmity. I doubt its related to the blm umbral tick but that is the only actual update to time scales we have recieved. The issue with peeling enemies off in the new dungeons though I think is a reflection of the strength of those mobs compared to previous so damage enmity compared to healing enmity healing enmity would be uneffected by the mob as it is generated with out influence from the mob.