I have two suggestions centered around the use of ground targeting skills. The first is if you have fast cast ground targeting off when you select a skill allow us to quickly deselect the skill with right click so that if we decide not to use the ability we can easily get rid of the ground targeting reticule.
The 2nd suggestion is when you have the fast cast ground targeting turned on. When you press the key to activate a ground targeted ability the reticule should appear while the keybind is held down. Then when you release the key the spell should fire at that point. This will give us the ability to line up our ground target abilities more accurately while still providing the speed and responsiveness that fast cast provides.