Using ground-targeted abilities like Flaming Arrow, Caster Limit Breaks, and pet placement are hard to use on a controller. They require too many button presses to fire the ability.

Use Ability -> Aim -> Deactivate Crosshotbar -> Hit X/A -> Ability Fires -> Reactivate Crosshotbar

There are work-arounds. You can omit a skill in the X/A button slot. You can hit Num0 or a mouse button with a pinky. None are ideal.

There are two ways that SE could implement a fix:

PRESS/PRESS
1. Hitting the GT ability button a second time activates the GT ability.

Ex: Hit GT Ability Button -> Aim -> Hit GT Ability Button Again -> GT Ability Fires

TAP/HOLD/RELEASE
2. Tapping the GT ability button fires the GT ability without aiming. Holding the button down allows the GT ability to be aimed. Releasing the button fires the GT ability.

Ex1: Hit GT Ability Button -> GT Ability Fires
Ex2: Hold GT Ability Button -> Aim -> Release GT Ability Button-> GT Ability Fires