If you are in the middle of any attack animation, you are incapable of activating any off-GCD abilities because your character is locked into that animation. As such, if you're hitting an off-GCD ability before you hit an attack button, you're queuing up the off-GCD to activate before the next animation so it resolves beforehand. If you use an off-GCD afterwards, on the other hand, it won't activate because you're already occupied. The only way to use multiple off-GCDs in quick succession is to not attack while you're busy clicking the lot of them and, even then, you'll have a slight wait between as each of their animations resolve before you can activate the next one.