It's not that balanced actually.
Eventually to min max, the path will be pretty straightfoward : more powerfull spell rather than more spells, and some spells will be so situational than they'll find themselves always picked last (O ye Rain...).
And the thing is, for a fight, there WILL be a combination of useful spells, so either you decide to have a lot of spell not to bother, either you'll min max it, and spend a lot of time switching spells between fights. I find this aspect boring rather than really interesting. There was a way to induce less options without requiring such a drastic change.
And I kind of like the idea of schools of skills in D:OS, I was psyched by the new schools like necromancer, now it does not have the same taste.
