Have you tried connecting to WOW using WTFast? You get a license for it for 6 months free and it really does help improve your latency and improve your connection stability.
Get the license key here: http://www.mweb.co.za/gamezone/?p=WTFast
and follow the instructions here:viewtopic.php?f=138&t=740
After you have downloaded and installed, here are a couple of tips for you:
1. You might be required to run WTFast in “administrator” mode for your PC, if this happens, just right click the application icon and select the option “Run as administrator”.
2. Once you are in WOW and running WTFast, you have reduce you ping even more by going to your WOW client “OPTIONS” -> ”NETWORK” and untick Optimise Network for speed. As WTFast is managing your connection, you don’t need the additional overhead created by this setting and it should improve your connections speed even further.