If you have the slaves limited to less than 15 FPS, that can cause follow issues.
I usually have mine capped at 20 FPS (slaves) and 60 FPS (master).

I've noticed a bit of extra lag, since Cataclysm launch.
Guessing just a lot more people on the servers.. since this includes toons still running Grizzly Hills dailies.
I just decided to turn settings down a little further on the slaves.