The original Elements were the best. But, since they're not a choice, I have to say Kelvena. As mentioned, she's the wisest and calmest; the best at keeping her head in a crisis, you could say. I also like Dominia, because she's an interesting character. Tolone and Seraphita just annoyed me.

As for Kelvena being blind, I remember reading somewhere that the reason she always has her eyes closed is to help control her overwhelming Ether power, or something like that. She does have her eyes open when she fights you, so it makes sense. (Sort of.)