Solution
I got this error months ago, but it seemed to be unsolvable. I eventually gave up .Recently However I was looking around and I saw that there are still people getting the error. I could never resolve the error, But finally I seem to Have hit upon a solution. Hope it works for you
1. Boot into safe mode with networking.
2.Disable Antivirus such as AVG
3.Turn on the launcher and even if it says lost connection to launcher, keep going until its fully downloaded
4.Then when its downloaded go into your warcraft folder and find the logs folder and go into the launcher log. Go down to the bottom of it and look for errors. What I found was:
09:15:37.9576 Updater error : There is no patch file to apply.
09:15:37.9576 Updater could not find the update mopaq at 'C:\Program Files (x86)\World of Warcraft\Updates\wow-13287-13316-Win-final.MPQ'
5. Then all I did was delete C:\Program Files (x86)\World of Warcraft\Updates\wow-13287-13316-Win-final.MPQ
6. Activate the launcher. The patch file that you have fully downloaded should install.
Hope it works for you. Took me months to find this. Could have beeen a localised issue on my computer but I felt that I should say it nonetheless. Good Luck
(This might be in the incorrect section for technical errors. Move if necessary)