dExtrosien
I agree that Raven is just dark. She went through a lot considering her crazy evil father. It is no surprised that she has shut herself off from the outside world, particulary to keep her enourmous power under control. There are plenty of good dark heroes, Batman comes to mind.
Bruce Wayne, Batman, suffered from depression and lack of love. Throughout the movies, comics, cartoons, and other things, Batman was afraid to love anyone, because they might be put in danger. That drove him into depression.
Back on subject, Raven is dark. She has just shut everyone away in order to control her powers. Raven has a great character flaw, which makes her human, even if we cannot send things flying through the air and levitate.
That is one reason I like TT. Each character has a flaw.
Robin: He is WAY overconfident and cocky. Also, he cares so much about Starfire he often makes hasty jugements.
Starfire: She is naive about Earth. She also has a problem of showing WAY too much compassion.
BB: He is an outcast. No one on the cartoon series likes him except for the Titans.
Cyborg: His lack of confidence in himself made him weak in the first few seasons. Then he became WAY too confident, and now he thinks he is all-powerful.
Raven: She has shut everyone away, and has severe emotion issues. If she was real she would be sterotyped as 'Goth' or 'Emo'.