my stratergy for beating him on masterful seemed to work, it only took one go, and I pwned the little bastard

, the stratergy was, run for the shock, ignore the 50a and always get the 100a, then you fight him, as he will always be at the 100a a little after it spawns, then run back up to the shock, you get the health up the top and down near the 100a, and you just hit him once or twice and hes dead anyway he will fall off.
stay around these areas and work on keeping your health, then when you see him then just pop him with the shock a few times, and then get more health. He got a bit ferocious, but just keep him at distance or spam him, you should be ok just be careful