Cooldowns and recast times are necessary, and a short "global" cooldown is a good idea so the game isn't spam-spam-spam. HOWEVER, it should not replace the recast time of a skill; it should only serve to separate the preceding skill from the one after it, and to that end it should be very short; all individual skills should all have their own recast/cooldown--not just the off-GCD ones.
The GCD in XIV seems to be trying to fulfill both purposes--the "recast" of a skill, and that separation between abilities. Therefore it is too long to feel comfortable as a separator, and too short to require any meaningful planning/strategy when using on-GCD skills.
Just my two cents. ^^;
