I've never downgraded. But anyways,
For PC. Open Start, My Computer, Local Disk(C:) , Program Files. World of Warcraft(Somewhere at the bottom, It's alphabetical). Then open the Data folder. enUS, find the one labeled realmlist.WTF or just realmlist. Then open it with notepad.
set realmlist undavosari.hopto.org
set patchlist undavosari.hopto.org
copy + paste that into the folder.Save, close, run wow. Type your account info for Vh and there ya go.