could be related to what people were saying about spellbreaker doing nothing to it as well (as spellbreaker would only block the spell damage and not tb)
unsure if that's new or not, but could be
tankbuster no longer is consider part of the ability taht triggers it its a seperate damage entity and does not interact with anything
before if you use tank buster with lash 3 you would heal the damage from tank buster, you dont do that anymore