Yup, you try playing a Monk and keep up GL with any kind of movement in the fight. You won't give two shits about GCD then, all you'll be worried about are those GL stacks.

Also, not to mention with all the movement monks do, the increase in the GCD makes it pretty rough to be flank/behind as your GCD comes up, espically on bigger mobs while avoiding shit without breaking your dps or missing a GCD. If your tank is moving around you can pretty much kiss your chance of doing full damage goodbye.

So yeah at 50 I'd say depending on class the GCD is really the least of your worries.