I've only ever had one that bit when broody. The worst I ever get from the others is a little fluff of the feathers and that errr sound they make. I can happily pat all mine on the nest and pick them up and move them without the slightest sign of aggression on their part.
Most of my broodies just tell you off but i do have the odd one that will bite scratch and literally try to kill you if she had a chance, i find they usually are the best mothers.