I am sorry but this is still casual difficulty, you just need to learn to tolerate a little failure, either on your part or on the part of other people for that matter.

This is a healthy difficulty. There's a smidge of resistance there, and all you need to do is pay a smidge of attention to the boss - Learn and then execute. It isn't surmountable for absolutely any player in this game, and nor is it asking for unrealistic expectations.