I do have to admit I didn't like Diana's character on the show. I don't know why the producers had her behaving like a jerk. One specific issue for me was disrespect toward Data (mispronouncing his name even after he corrects her really irked me). He was an officer and he should have been treated accordingly.
Anyway, I do agree that Crusher didn't have much of a personality. Which is probably why Marina liked Gates. They and their characters had a lot in common.