And then can't tell whether the vector it's projecting for you is including moving your character or not - because you can't see them both at once, and the game might or might not be auto-moving your character as part of targeting that enemy, with no way of knowing - because if you slide the camera back to check, you're no longer mousing the intended target! Thanks Larian! Professional design!
Well ... personaly i solve this by rotating the camera and adjusting the angle so i see both my character, and the enemy.

So far i didnt find any place where that would be impossible (except for spiders cave, when you are down and spider several levels abowe you ... that place was a horror in previous patches ... not sure how it works now since it is quite long when this situation happened to me last time)
But yes, this problem should certainly be Adressed ...
I believe i have seen some suggestion ... it was some kind of warning sign, either with alterning collor of your cursor ... or adding message "movement required" or something simmilar, to your cursor when you are aiming the spell.
I liked it both.