At the same time, I don't have a good explanation for why he did rape her. I can't excuse him for this act. And, sorry, I don't buy the Raver theory at all. There is no evidence at all that a Raver was involved.
Some of your suggestions that I took notice of:
she tells him that his reality is unreal, and that his dream is reality. Without realizing it, she challenges his sanity just as surely as Lord Foul did. And so he attacks her.
I would have to agree with Mhorham and Nerdanel about TC. He committed the rape - not a raver. I always saw it as this way: Here is Lena, a beautiful young girl who no less than worships TC. Adoration oozes from her and TC cannot handle it after all the months of human rejection because of his leporsy. Also, the fact that he has been impotent for so long and now can suddenly "perform", it becomes more than he can control. TC simply loses control of himself. Unfortunately, Lena pays the price.
All of these are good comments, but they don't explain to me really why he loses control. I guess I think a person should be able to control himself.Most people have a bit of darkness in them -- jealousy, anger, spite, whatever. And most manage to keep it locked up. It's when they lose control when bad things like murder and rape happen.
~MsMary~