Yes I know about those, but its not really comfortable to use it right, you probably know yourself. Selecting alliance member with L1 and Left/Right will lose its soft selection the moment you press a skill, so you lose some seconds going through it spamming it, until you hard select it, but oh boi you wanna heal yourself too? You would have to use something like /targetlasttarget to get back to it fast, but that is very awkward.
Essentially, it just needs an option to cycle through alliance members that isn't using the left thumb of your hand. (Or you would have to use your right thumb to control the left stick, or use your index finger for D-Pad which is very strange too and not suitable for longer duration)
They even have it for keyboard. They just didn't map it to controller. Or at least giving us an option to assign it.
In the end it screams like using a custom tool/driver for controller that lets you assign hotkeys differently, than the games standard layout.