If you use addons that communicate over the addon channel and use ChatThrottleLib (which most addons should use), you will find that the addon messages between wow clients are further throttled when the fps is below 15. In order to get "full speed" addon communication I recommend a minimum FPS of 15 (or is it 16?).

Source: the source code for ChatThrottleLib.

http://www.wowwiki.com/ChatThrottleLib