Another issue with Ekko is his W isn't punishing if you miss it

First of all its a shield second of all there is a period of time after it lands where ekko can still trigger the stun,now the issue? The slow occurs before it lands which is fine if he wasn't building tank,the period of time where he can trigger the stun is far to long that it isn't punishing if he misses the landing

solution? reduce that period of time where he can trigger the stun by 0.25 seconds or 0.5 seconds,preferably 0.25 seconds so the casual AP ekko isn't hit so hard

EDIT:period of time where he is allowed to stun increases with per 100 AP increasing the period of time by .15 seconds capped at 0.25