I was actually going to mention that as well. It's like the end of the game suddenly turned into god of war. What annoys me about that "boss" battle is that you spend most of the time fighting his summoned minions. I get a bit annoyed when a final boss does that. You already spend a good portion of the game fighting Bloodletters and Chaos Space Marines, yet you got to do it again, because Nemeroth is too much of a wimp to fight directly.
Another disappointing final boss fight, that I remember, is from Knights of the Temple II. All you do is attack and destroy three statues, which can take less than a minute. Then, you attack the boss (can't remember his name) by basically button smashing, so long as you keep your stamina bar refilled with potions.