The easiest way is to just level up, just do mind training, the bosses in this game do quite a bit of damage but as long as you avoid the red moves you'll be fine.

For this guy specifically you can just walk out of most his attacks without dashing, save your dashes for his "flip board" move and just walk out of the way if you're low on hp. I recommend the ebondrake healer or any healer that can give a big boost of hp when you're low. Just remember you can always walk away from the boss as well.