Kennen W bug, or clarity update

I am not certain if it is a 'bug' but it seems odd for his gameplay.

If Kennen has a mark of the storm on an enemy in range it is the only time you can press W.

Here is the scenario that creates the problem:

You shuriken/auto attack to apply a mark of the storm at max range to your lane opponent. You want to follow up with a W. So you move toward the enemy, as they are moving away. 'W' lights up as you hit max range...but the enemy is still moving away.

You activate W, causing Kennen to temporarily stop. The ability goes on CD, the Sound effect Plays...but the enemy keeps moving in that .2 of a second causing them to be out of range...so the effect doesn't go off.

I feel like this ability could be cleaned up with some of the logic/coding that applies to the newer champs to judge that distance faster...or real time. Having the ability go on CD and the Sound Effect playing is confusing.

Usually you don't notice the bug, since it is only easy to notice when you only have one target with Mark of the Storm up. Since I am usually trying to bully my top lane opponent I freeze my lane, making it very obvious when it happens as my 'W' has no other target to go after.

If you have further questions or want a video of it happening, let me know.

Thank you!