True though Avatar is half Anime, but that doesn't mean anything. Today we have improved on the always casting ugly people as villains. But there was a time when that was the case in my opinion, the 1980's Disney cartoons was quilty of that, though once in a while they would throw you a attractive villain, it inforced that the ugly people are the bad guys.
Avatar is a very deep and enlighted show, unfortuntely there are few shows like Avatar. Except for Ozai and maybe Azula, there are no clear cut villains, the show is full of gray characters.
I agree with you about those three girls being attractive especially Azula. I think Azula is very hot. While she is a horrible person, she is very attractive, I give the demon that. Though despite her hotness, she scares me at times, she is very intimating. Azula is scarer than any ugly animated witch. One of the things I am looking forward to in the Avatar movies, is seeing the live action version of the girls.