If you are getting the error message
Failed to download a required installation file (http://ak.worldofwarcraft.com.edgesuite.net/wow-pod/installdata/win/wow_enus_web_unencrypted_win.blob). Please check your internet connection and try again.
then simply rename your installation file WoW-5.0.0-Beta-enGB-Installer to World of Warcraft Beta Setup
This works for enus, ruru, engb, dede, frfr, itit, and so on.
Have fun playing the new World of Warcraft : Mist of Pandaria .
Yes, this is the leaked Beta client No, I’m not sharing any info (yet). Hint: Russians!
Blue post, Beta technical support