Tip for Hunters if you havin trouble on them on legendary
one pistol shot to the orange part on their back/neck/belly will kill them, either move towards them, then shoot the stomach after they try to melee you with their shield, or jump at them, they will bash you into the air, then turn around in mid air and shot their back with the pistol
its epic
or...one close range shotgun blast to the stomach will finish thm off
or a sniper shot to the orange parts