tl;dr Boss fights suck.
This game is pretty simple, get from point A to point B while slaughtering, surviving and collecting stuff. You are doing all this while looking for tomes, deciding to pick grims and wondering if you should use the healing now or if you are going to die during next wave.
And then boom, boss out of nowhere, in small, empty, locked arena, theres something that just stands there and waits for you to kill it. Bosses often cant even follow you around, they dont have control of their own arena. Completely ruins whole pace of the game, isnt challenging or tactical.
Boss battles were good idea but were poorly executed.
What is the best boss fight in V2? Getting attacked by stormfiend while we were destroying the bell was better than any of the 4 boss fights. You had big, open, multileveled arena, there was other objective aside from boss and the fiend could follow you everywhere + stormfiends look really cool.