Wow! Very nice post.
Very detailed, insightful and well thought. Even though I haven't tested out most things that you talked about, I have a strong feeling that you're right. Also the spells sound quite varied and interesting. I expect investing points into new skills to be a lot of fun in this game.
It's interesting how the Spirit mastery helps make both the best Defensive character (Spirit + Defense), as well as the most effective damage dealer (Spirit + Earth).
I'd love to see a description of the Hunter mastery, what it is best for, and with which mastery it works the best.
Again, fantastic job with your description. I'm impressed!
P.S. I still prefer the Storm mastery. I guess I've always been more interested in lighting than fire. (same thing happened with Diablo 2 and Dungeon Siege)
P.P.S. What is your first character going to be? Mine Defense + Spirit.