its very simple, FFXIV every check is done on the server. when the cast ends, where the server thinks you are is how it calculates if you are hit or not. It does not matter what you see on your screen, if your updated position has not hit the server (ISP lag or w/e other reason may slow it down) you get hit. WoW does these checks on the client and then passes to the server if you were hit, making what you see what happens. The client side checks are nicer for the gamer, but are susceptible to hacking to say you evaded wen you didn't. SE took the easy path of making the server do it to ensure this can not happen, and it has its downsides.