When you don't have TE, all that a vibration dampener does is control sound.
But once you have developed TE, then your elbow becomes extremely sensitive to the string vibration, and my experience tells me that it can aggrevate the TE.
I don't know if you people have tried Babolat Racket Vibration System (RVS). TW sells it for a few bucks, and this product claims that it not only dampens string vibration but also the frame vibration (which is a whole lot more important for TE sufferers).
I was skeptical at first, but I tried it. It made a believer out of me.