Mao certainly is not unbeatable. Remember, she only won her World title by 1 point last season. Carolina was only 1 point behind and Yu-Na was only 2 points behind. Asada has been beaten by Kim on numerous occasions and by Ando.
Though I agree with you, however when I consider the recent 2 years, I would say if Mao has a clean programme, Joannie can hardly BEAT her. I think the probability Joannie wins may be that Mao falls at least once while Joannie has flawless programmes. Another question is whether Mao still flutz or not