I still can't beat Ishann on NG+ after more than a week. It's that damn spear and even with consumables my posture is too weak to stay close to him which was my winning stretegy first time round. I've thought about restarting the game and avoiding skills just to stack on the mask to get the ending trophies but getting back to 20 VIT would be such a pain and it would leave me having to replay the game against to grind the skills for those trophies. Fuck this boss.
Everything in the above reply is my opinion, from my own perspective and not representative of reality outside of my own head!
-Android user, please be gentle with critique on my spelling.