Quote Originally Posted by AscendantManes View Post
...okay, but seriously. This idea only dawned on me after uninstalling and reinstalling, but maybe you can make a backup of the entire game minus the launcher and boot, and reinstalling into that? I'm not sure how to explain that well.
Nope, but what you can do is if you have a friend with a working installation, they can zip their "C:\Program Files (x86)\SquareEnix\SquareEnix\FINAL FANTASY XIV - A Realm Reborn\boot" (location assumes a standard non-Steam PC installation) directory and send it to you.

Make a backup of or rename your boot directory just in case, and unzip the one they sent you at the proper location. It fixed my client, and I even used a copy of the Steam boot folder on my regular non-Steam installation.