The 0.3s check itself is not a problem. The problem is that the client in this game does no real work and has no authority. In any other game, what happens is server tells client "AE coming in 2.0s", and client knows when the AE ends, and it definitely knows the position of the player at that point, so it either tells servers "Player avoided AE!" or "Player got hit" depending on what it sees. It doesn't matter how much lag there is between the client and the server, because the client knows when the AE ends, and it definitely knows where the player is. The info can be incredibly delayed but it'll still match what you observe on your screen. In FF14, the 'Player got hit' decision is made by the server. All the client does is relay the player's position at certain times. Even though the client has a better picture of the player's position, it doesn't matter.