The fix is apparently as easy as changing a "true" statement to "false" in the ffxigame.exe code lol. Anyway heres the link. Keep in mind this fix only works for this specific patch version. You must backup your ffxigame.exe (just create a copy of it) before patching, and replace it when the game gets patched again. This guy has been updating every patch its not big deal.
This makes the mouse completely lagless and awesome, the game is actually pretty playable now!