There have been a few times I have noticed in arena as well as trash mobs on fire knight where his a3 which reads "will ignore unkillable and block damage buffs" has actually been blocked by those buffs. I have noticed a few times specifically against skullcrown and skullcrusher this has happened. the few times this has happened to be the rival mob was at 1 health with the buff up and nothing happened with the execute. I have also noticed on other times where if the mob is low health and the execute goes off proccing the unkillable/block damage buff that the mob will stay alive even though there is a block revive if killed function of the execute. I don't know if that last part of the mechanic is supposed to happen like that but the other times for sure it should have worked. just something I have noticed.