Whenever I see a magic system I'm always interested in how the writer explains the sociological implications of it. Like, what determines if a person is a Sorcerer or not? Is it a hereditary part of their bloodline, an outside force granting them powers or is it a skill that anyone can pick up with practice? I've always found the popular notion prevalent in fantasy that magic is privy only to a select group of ubermensch as boring and overused. Yeah we get it, magic flows in your veins or perhaps you have a sixth sense or something, making you automatically superior to most other characters you come across. As I said, boooring. (that's just my opinion in general, not slagging off anything in particular) 

So yeah, when it comes to your system, I'd like to see an explanation about what makes one a Sorcerer and how it sets them apart from others. Sure, you can always say that it's "just magic, it happens", but since you're already going fairly in-depth with the system, I don't see why you shouldn't touch upon this as well. 

Another thing, apart from mental exhaustion and such, usually there is some sort of price/restriction associated with spell-casting so that it remains somewhat balanced and interesting, otherwise people can just use magic willy-nilly to solve all their problems. Tolkien keeps magic users rare and the whole thing is shrouded in mystery, it's not something that the Fellowship can call upon at any time; George Martin uses blood magic and the idea that you have to give up a life in return for power; Dragon Age has these demons in the Fade that can take over your body if you're not careful (as well as blood magic, which seems like a popular concept these days); the Source in Jordan's Wheel of Time can burn you out if you draw too much; Brandon Sanderson's magic in Mistborn uses metals as a fuel and so forth. These are just at the top of my head, but I think it's important to have some drawback to using magic, because this keeps it interesting for the readers. 

Also, since I mentioned Sanderson, I wholeheartedly recommend you check out his magic systems, he's one of the best in the game when it comes to that sort of stuff.