Quote Originally Posted by KisaiTenshi View Post
Supposedly you should only need to download http://www.finalfantasyxiv.com/playersdownload/na/ that again, as it will update the launcher first. It isn't supposed to overwrite newer files with older ones. If people think they have to download 17GB, then they likely uninstalled the entire game first.

If it's like any other MMO, all you really need to do is roll-back the version number.
eg go to
C:\Program Files (x86)\SquareEnix\FINAL FANTASY XIV - A Realm Reborn\boot
Open ffxivboot.ver and see if it has 2015.05.20.0000.0001 in it.
This helped, thank you!