When Darth Vader uses his Merciless Massacre Ability on auto, if there is an enemy that is taunting, Vader will prioritise that enemy and will not target any other enemies. This in turn limits the damage done to the enemy team but also the cooldown to use this ability again.
It doesn't seem like this affects Vader when he is on defence but have only tested this through conquest as I don't see too much of Vader on defence in GAC or TW.
