Are bosses intended to be this hard while leveling

Or do I just have a bad spec? I’m a level 49 permafrost bolt build witch hunter, stuck on The Prisoner in act IV. I feel like it takes forever to whittle down a boss, I just can’t tell if it’s bad skill or I’m doing it right and it’s just meant to be this way. I haven’t tried any other classes yet to see if there’s a difference.