Well in most games difficulty comes from number, toughness, and abilities of your enemies. Difficulty can also come from watering down the player character's abilities. Difficulty should not come from randomly getting stuck on objects in the environment or not being able to move (both of which happen in this game through what can only be described as glitches, not gameplay). It also should not come from abilities for which there is no defense.

I guess you could call his hammerfists an "ability" except that there's no defense for them and he can unleash them any time he wants, including while you're shooting him (which normally disrupts his attack and occupies him for a few seconds) and while he's doing other things (giving you the sense that you have time to move to evade his next attack). He shouldn't be able to cast a spell and mid-casting stop and hammerfist you. He also shouldn't be able to recover so quickly from being shot to hammerfist you, as at other times shooting him gives you more time to act. I also got hammerfisted twice in a row in 5 seconds, and considering your character can't move or do anything while you recover from each hit, and that you die from 2 such attacks even if you have 100% health, it's a pretty shitty way to make a game "difficult."