Well, we have clocked up Jack, Mickey and (arguably) Adam in the space of two seasons, after no male companions since Turlough, so we aren't doing too badly! The girls get characterised a bit randomly sometimes, I think: even hardcore women like Leela and Ace have to 'be in peril and need rescuing' because that's the nature of the show, and some writers are better at keeping that in character than others. If the companions are too capable, there's not enough left for the Doctor to do.

The Master is always the best thing about anything :)