Can We Change that...

[Nyaanyaa]

Use mouseover <mo>

That's a workaround, not a solution, and a dirty one at that. Using <mo> will not allow you to use your mouse in other ways while selecting targets/casting spells, e.g. you couldn't use it to rotate your camera at the same time.

Get a Razer naga 12 button mouse
Left hand sits on W A S D for dodging etc.
Right hand hovers mouse over party list
Right thumb for casting everything and easy mode

I'm sorry, but that has nothing to do with anything in this thread.