I've noticed that the implementation of this is extremely sloppy. There is lag so when you stop and cast a spell the server still thinks you're running and you won't cast anything. In moments like that you are not sure to hit the button again because is the server really casting your spell, or will the next button press cancel it? I've been standing still pressing the button 3 or 4 times trying to get something to register on my screen, just so I can heal somebody.

That's unacceptable. In WoW, you can cast instant cast spells while moving all day long. If you're moving and you stop and start casting a spell with a cast time, you get instant feedback that you're casting with a cast bar, and you always cast your spell immediately when you stop moving. In FFXIV, it is so sloppy.

They should go back to how it was until version 2.0.