In my case it happened to Asus Cerberus Mech RGB keyboard and Microsoft Edge.
I updated windows,driver,firmware and everything this problem persisting on me for a year.
Until few days ago I updated my edge to edge chromium stable version.
All delay and the lag that happening while I'm using skills all gone I can spam as fast as I suppose to.
So I suggest you updated your edge to edge chromium or use chrome instead while playing Aion.
Sometimes things that seems totally unrelated affected each other
I hope it helps if anyone having this kind or similar problems thank you and cya