I'm agreeing with Reader on this one. It seems that all skills that are off of the global cooldown are still ruled by animations. You cannot use an off-the-GCD skill until the animation of the skill previously used has finished. And any other skill used after an off-the-GCD must still wait for the animation of said skill to complete.
I agree with you Naks that this just feels wrong, as I am very accustomed to playing games where the animations for many skills can be clipped short to perform the next move. But, since it appears to be a universal issue for all classes I've played, I'm also leaning on the "it's intentional, not a bug" side of the fence, and will simply learn how to play through it.
Although, once they can find a way to keep the servers from flopping around like Magikarps, I'd love to see this discussion brought up again