The game throws big bosses at you at a time when you won't have range weapons, and expects you to dodge these big sweeping attacks that would be more appropriate fighting with ranged weapons. And by the time you get a ranged weapon, it's too late, and they've raised the stakes again for future bosses to the point that having a ranged weapon isn't even an advantage.

I was forced to reduce the difficulty just for the bosses. All of the other enemies were mostly fine.