There have been calls to lower the GCD since the Beta test, and SE even back then stated flatly, "No". So it's pretty clear they're set on keeping the GCD as it is I'm afraid.

And really, it's not that bad, you just have to stop treating the game as an action game and not button-mash, the GCD is a rough analogy to the classic ATB gauge from past FF games. Time your button hits and the GCD should not be a problem.