Uhn. You need to wait half of a second between letting go of the control stick and confirming the target of your spell, you will also not simply loose your spell to the cancelling effect because it doesn't lets you start casting while moving, so it's easy enough to adapt to this by simply doing what we all did (or at least I did) before action queuing came by, hitting the button until the ability goes off.

I admit this game is pretty fast but not as fast as that little action getting in the way of anything. Unless i'm wrong, I haven't done Ifrit or Moogle yet, so.

Also, before you say it, the 'brake' button is not lagless at all, it has the exact same lag letting go of the directional button, it does gives a better synchronization between server and client because the client assures the server of wtf is going on at the screen. Depending on what gets judged by the server as correct, you will either be 'lag-jumping' in other player's screens or you will get corrected in your own screen if you're suffering from heavy lag. It's not as much a panacea as it seems.

Disclaimer: My technical knowledge is very small, I could be wrong in all this, it's just suppositions