I'm torn on mr x. On one hand, during my first playthrough on HC, I had a few moments where he showed up and while not fucking me himself, he made me run in front of lickers or rush into a room full of zombies which ultimately lead to my death. That's good! On the other hand, on many other occasions he was just annoying and I had to lure him out of a puzzle room (e.g. library), cheese him around the stairs and back to library. I think a better approach would be to have him appear in scripted moments with some randomness thrown in, so that in one run he shows up in a certain place and in other he doesn't. Also he should be 'killable' like Nemesis was in RE3 - down him, he drops something and then he doesn't reappear until next major plot point or something. So yeah, it's a mixed bag but I do think that even in his current state, it's better for mr x to be there than if he wouldn't be in the game at all.