Thats normal, i did played it on hardmode aswell. If you use counter attack items you should be fine.
Also if you have difficulty with this boss try this:
Once you have the bunny ears to make yourself quick, give it to Ray with other speed up items and counter attack items. Look at my screen of the items Ray holds. You can cast Immortality on yourself and let the enemies kill them selves due your couter attack! (if you are faster then the bosses you can cast Immortality on Ray before it ends
View attachment 2940602