He's way harder in NG. I fought him in NG++ and in NG on different characters, and in NG++ he still hits like a truck, but he dies much, much faster because your character is so strong by then (so I imagine it's similar in NG+, I wasn't that much stronger in NG++ than NG+ myself).
In NG I had only a +6 weapon too and did rather weak damage, had to rely on viscerals because normal hits or a combo would risk me being parried, it was way more dangerous, and his gun took off most of my health if I got hit. I died once or twice only in NG++, but repeatedly in NG.
Try him in NG some time, it's fun.
One of the most challenging fights of the game.