I had the file "wow-0-16309-Win-final.MPQ" that I kept deleting and redownloading in hopes that it would fix my launcher problems, but it didn't. My sister, however, was able to log into WoW for the past five hours and I wasn't sure why. I asked her to send me her update file through Skype. Evidently, she didn't have "wow-0-16309-Win-final.MPQ"... but "wow-0-16357-Win-final.MPQ". She sent me it and I opened the launcher. After a very, very short patch (only about 3-5 seconds of downloading), I can get into the game now!
I don't know if we're allowed to link downloads on this forum or anything even though I read through the rules, but try this fix if you're having the same launcher-leading-to-launcher issues that I was.