Also, I have another point to make. Using the scroll wheel to change spells is awful, because if you are on a laptop you simply do not have a scroll whell. Perhaps using the number keys to switch to specific spells might be better?
Just because you cannot play Counterstrike or League of Legends without an external mouse, that doesn't mean that game developers don't think about these kinds of things. I myself have been creating video games for over a year and I design them to be friendly to touchpads and external mice. If you design around the constraints of touchpads, laptop users don't have to suffer.