Played controller on XIV for years. Still do, its chill and can clear end-game content fine with it. In fact the developers when testing the game (at least up to Heavensward) always tested it with controller in mind first, since its the one common interface all players have access to (due to console) while that's not necessarily the case for mouse/keyboard. The 2.5 gcd to 1.5 being a problem is also a slight myth/misgnomer as certain classes have a significant amount of oGCD actions that can make them as speedy as a WoW class. The highest was ninja at 49 or so, tho it did get trimmed a little. But still, that's within one third of the dps specs of the game right there. (Obviously not close to extremes like Fury or Brewmaster)
Also there's just significantly more abilities in XIV to bind, and yet there was more than enough binds to comfortably do everything. So WoW won't be a problem in that regard either. If anything it'll be super easy to set up. Also encounter design is pretty different between the two games; FFXIV fights have significantly more movement involved for their raids for everyone involved. Either because of the GCD or simply because it does, one or the other. Segments often target everyone, albeit maybe targeting everyone with something different. While WoW mechanics are deadly and usually require an immediate response, they also tend to target less people at a time in most encounters, so more button mashing your rotation feels fine here too.
My biggest concern for me is to why I feel WoW would be a bust controller wise is XIV's controller scheme working is contingent on legacy movement. What that is for people who do not play XIV on controller or have never messed with options in the game is when you say, press S, you don't back pedal and instead your character immediately faces/snaps south and runs that direction on a dime. Its the difference between DotA having a turn speed or League having no turn-speed at all. Because of this, movement on controller is responsive since you can run diagonally backwards at full speed because you face that direction immediately. No camera panning required unless you feel like you need visibility in that direction. The camera is not your 'head' in terms of movement.
That said by default the movement if you play with a mouse and keyboard is WoW-like; press S and you backpedal. Controller turns that off because it wisely knows it'll be an issue. Furthermore, mouse and keyboard players have the option to turn legacy movement on so that it doesn't become a controller advantage if they don't want to deal with camera manipulation for forward/strafe movement. Unless WoW intends to allow this kind of movement backpedaling will be hard to avoid on a controller and give very stiff responses to getting out of bad. On the other hand if they enable legacy on just controller, I would see that as a legitimate thing for non-controller users to complain about because although most of us are used to the "techniques" it takes for running a certain direction (jumping while strafing, quick camera spins while strafing/forward, etc.) I think a lot of people take for granted how much of that is muscle memory from playing the game for years. After all, you still see some people backpedaling.