Shortening the GCD probably wouldn't work either.

It's not that WoW is super fast, it's just far smoother. Abilities flow without that short server lag. Even if you macro 4 off-gcd's together, they all trigger instantly. If you press a button slightly too fast it simply queue's and flows after your current action. In ff14 however, sometimes you fire 3 Ninjitsu off and the server chokes, lags up and fails to register the 3rd one until you press again and end up with a bunny on your head.

FF14 servers simply aren't capable of faster or smoother combat.