The delay from skills here come fro 2 points:

1- Usually players use heavy stanmina cost skills without having any stanmina so you have to wait the gauge fill.
2- The game use a action pile of 3 actions. If you send too many actions you will have some stored that will need to be executed before the one you actually want.

I already suggested them that the pile start giving newest actions priority over older ones so the response to actions would improve alot. Hopefully they will listen to this.