Now that is some made up bullshit
So just because some of them are deformed as fuck that does not mean it is due the chakra nature. There are other fucked up characters with different nature(s). Since not all of the users are deformed your point is invalid. Those powers are mainly inherited by the clans, so they are not ugly as fuck due their nature, but because of their heritage. In case of the named characters, obviously you brought up personal opinions that questions your post's validity.
Sakura: She is useless, due she could never really explore her real strength. She simply learned other things, which has nothing to do with her chakra natures. It was she, who fucked it up. In this case earth nature can not be blamed.
Kiba: He can cast earth typed without his dog too. Although, it is not that strong, but again it's not because of the chakra nature. His clan is based on companions, like K9 units in real life. Not so effective alone, but it is due the clan's methods. (that 3 headed wolf thing did not look bad, whether it was impressive or not that is just personal opinion)
Rock Lee: Earth nature is complicated, that is why its rare. He was not able to master it, because he sucked at ninjutsu. He was simply not enough for that, that's it.
About the mutants:
Don't think natures have anything to do with ugly faces. Akatsuchi is simply large and fat, of course he has a weird face. In mangas and animes fat people have such face. Not to mention there is only one character who has awkwardly small size, so reasoning like that, because of ONE out of many, can not support your reason. In case of Mu you see bandages only, but we do not really know why is that. It could be his style or a simple injury. Yeah, Deidara is one fucked up character, but he is the only one, whose mutation can not be explained really.
So, I do not agree, due most of your points are invalid.I'd rather say Earth type is complicated, but not an illness. Those who look ugly simply went too far with their technics, but that would probably happen in case of every nature too.
Here is some potato for reading it (that also grows in earth)
Follow @SLO_MMORPG