Hmm...Like Light, Air is virtually everywhere too. So that should be taken into consideration. Since you're going with a blood system..it seems like the water mages would have an edge over everyone. Unless you add something like natural aura keeping a person's inner body protected, water mages could easily interfere with the magic of all the other classes by messing with their blood. I was going to bring that up. Plus if you bend light you can get a makeshift invisibility. And if you keep light from hitting the eyeballs of your enemies, you've effectively blinded them. All kinds of uses for Light Magic that can be devastating.