Enemy AI is kind of...varying?
The enemy AI didn't seem to be increasing at a set pase through the story mode. For example, I couldn't even hurt Alucard until I backed him into a corner and kickd the crap out of him, but Cyclops was a complete wuss.
That's the second problem. Something needs to be done about how you can easily win if you simply back the opponent into a corner and kick the shit out of them. Perhaps, you could put in a "knockdown" system, where, after a combo, the character would be knocked down, and be given a period of invulnerability to let them avoid the easy death by corner+foot.