Why a global cool down?

1) It doesn't balance anything, because it applies to everybody.
2) It makes combos nearly impossible.
3) Plenty of other ways to buff/nerf things.
- (PvE) Increase the hp, dmg, and defense of mobs & also add new def/offensive abilities. Add de-buffs to players when entering a more difficult encounter.
- (PvP) Make it easier to farm high quality gear. Adjust dmg output scaling. Add vulnerability after x amount of time/kills.
4)All spells & abilities are instant cast, add in latency, throw in GCD, and you have a headache.
5) A GCD on buffs? Takes a mage a good 3 or 4 seconds to buff. Which by that time his whole party just died & or he lost the duel.

Conclusion:

A GCD mostly forces users to button mash their touch screens so they can get off an ability as soon as its ready. Before, it was a battle of quickness of mind, combo decisions, split second buffs! Reaction times were everything, and it was exhilarating!
Now, one spends more time on tapping their touch screen than they do on actual game-play. Or to even enjoy the game, the environment, and community...
To be honest, I feel confident that these problems will be addressed. It would be pure negligence otherwise, and I have faith that these Devs aren't like that. They did make a freakin' awesome game, remember...