I will try to put the range of the skill to max, so that the caster won't move when casting.
Edit : so I tried to mod Meteor Rain, I don't know how to make it without a targeting click in normal cast.
But with increasing the "range" of the skill, if you don't zoom out to the max, the char won't move in quickcast.
Reducing the offset from 20 to 8 seems to give a good compromise between randomness and precision.