Can you please provide photo or video evidence of him getting double or triple protection back before you have reinforced? Because that has not been the case for some time (it's the 2nd iteration of the bug that was fixed at least a couple weeks ago).
As for how to beat him - focus fire, good ship synergy that includes enough damage to kill him, not reinforcing until he's dead. I usually leave him alone until his first taunt because I don't want to give him any more health than I have to (him healing is essentially extending his total health pool), and then once I'm forced to shoot at him for a bit I focus him down quickly.