Null Field
i think you might be pressing other buttons before you land the null field, look if you press the null field button and before you click the ground target, you go and press another button, the target will disapear… not sure if this is what happens to you.
I eventually found that clicking the skill then casting the reticle was awkward at times. I solved my problem by binding it to any of your neighbouring buttons around WASD. It makes things easier when you don’t have to drag your mouse around as much
Don’t click cast spells. Use hotkeys. I personally use the default 1-5 for weapons and my naga mouse for keys 6-0. Since you can hit the key and already have your mouse positioned to cast the aoe it makes things faster.
In addition, there is an option to quick cast AoEs at your mouse location in settings. Personally, I find that I need to be able to see the reticle in order to land Time Warp to account for varied ally positions so I don’t use it. But you can still mimic quick casting by tapping your hotkey twice. The first hit pulls up the reticle, the second casts it where the mouse is.