I don't know about the benefits of achieving maximum "deadness". I've run some informal experiments using different damping materials on my TT's plinth. I definitely found thet there is a point where there is too much deadening which sucks the life out of the music. Yes, you have to address gross vibrations and such, that's not what I'm talking about. AFTER you have got is pretty right this is the fine tuning. Just don't over do it.
Bob
Bob