Does the lag eventually settle down on your box? What I mean is, does it only lag for the first 30-seconds to a minute, mostly? If it lags constantly the entire time you're there no matter how long you sit there, then the symlinking will probably not help you. For those of us that lag badly for a few seconds and then see it clear up, this indicates that it only lags while textures/models are loaded from the hard disk, which symlinking greatly helps with. For constant lag, that's an indication that your system just doesn't have the horsepower (or interwebz speed) to handle the constant activity there.

That's my nickel explanation, anyway.

[edit]
Oh, and regarding symlinking, I would use a junction linking tool like Winbolic or JunctionMagic to do it with and (most importantly) experiment on another test directory FIRST before you do it with your wow folders.