It would be nice if there was also a way to activate your active ability using the keyboard rather than the mouse.
That would probably be much more annoying than using a mouse when having to target specific squares. Sure, it would be great for activating buffs, but it would be really frustrating when you're trying to get the cursor to land on your target.
This would be in addition to, not in place of, the existing right-click activation. (You're right though, it would mainly just be good for buffs)