@taboo:
Zabuza and Haku died~ And some of the lesser villians like the Sound 4, and Dosu.
Mentioning Haku/Zabuza almost makes me think of an entirely different series; they were the only major antagonists before Sasori to die and their deaths left an actual "hole", that is, Zabuza was one of the "Seven Sword Shinobi of the Mist" and there are only six left now.
Sasori's "hole" was filled, Dosu/nameless Grass Genin/nameless Rain Genin/Kin/Zaku/Chiyo are all relatively minor as far as the scope of the main storyline go, for they only appeared in a certain arc and died in the same one.
Yondaime's death was the first significant Naruto death, and he left a "hole" when he died; Asuma? He was the most minor of the Rookie 9 instructors and didn't shine until this mission. He's basically in the same category as Chiyo; basically nothing, with a death that accomplished nothing as far as the main story is concerned.