It's the combination of weight and flexibility isn't it? As I understand it flexible racquets transmit less initial shock, but vibrate for longer, and at lower amplitude? Weight helps, as you say, to dissipate the vibration, so a heavy and flexible racquet ought to reduce both shock and viration I think. But some people do seem to find those low frequency vibrations annoying. I had a very flexible (but also fairly light) racquet that had horrible vibrations and caused me some arm problems, though I think partly because the flex contributed to the low power, which also led me to over-hit.
I'm currently using a Gravity S, which is pretty flexible and low-impact, but at stock weight (300g strung) there are certainly some residual vibrations. However, if you add weight (I've tried going up to 330g) the vibration noticeably decreases. But you need both weight and flex: I've a 360g+ Head Ventoris 660 that isn't exactly stiff, but is heavy and does vibrate quite a bit.
The Pro Kennex formula for many of their racquets seems to be to have realtively stiff frames, which won't vibrate for long, but with the kinetic material to dampen the shock. I haven't hit one yet and am keen to try, though I'm leaning more towards their slightly more flexible offernigs.
