I'd like to recommend Leatrix Latency Fix for everyone out there. It's an addon/mod that increases the frequency of TCP acknowledgments sent to the game server. (reducing your MS/latency).
It'll reduce your MS with about 66% in the most cases. Personally I went from 250-280 to 80-110 (110 is in WG and dalaran at peak times).
If this sounds temping; follow the link below and click "Download" at the top right corner. Install it and restart your computer!
http://www.wowinterface.com/downloads/info13581-LeatrixLatencyFix.htmlEnjoy reduced latency!