From your own OP:
"water main is decent and can be awesome with cc and effects team or crazy heals were u cant kill them"

And as other people brought up, the mains don't exist in a vacuum. They need to be balanced against the other mains on the basis of what teams they can be used to form. I'm not saying all the mains are perfectly balanced, but every main can make a viable team.

"Please tell me were earth main fits in this equation?"
As a support ninja, providing shields and/or a tanky body for your team.