That's a good point, though BtVS was always to some extent idea-driven - hell, taking Joss' oft-quoted inspirational idea of the little blonde girl in the alley kicking the monster's ass, the entire premise of the show is - and that didn't usually stop them from making the characters more or less distinct and consistent before. Maybe the comics are simply too one-dimensional to have BOTH ideas, plots, and characterizations, but...