I don't think tuners are about dampening vibrations as much as they are about changing the location of the nodes so the muzzle is at the center of a vibrational node...ie- not moving when the bullet exits. The particle dampening tuners I have don't seem to work any different than the solid mass tuners. They both are equally effective for what we are trying to accomplish.
The way I am visualizing the dampening of the harmonic vibrations is that the damping action lowers the peaks or amplitudes of the sin waves, and elongates the waves as well. So, the lower the amplitude of the waves, the easier it is for the muzzle to stay closer to center, and the nodes will be longer and more room inbetween them because the wave is flattened and elongated and the peakiness of the amplitude is clipped. That is the way I think it works, though I am not a harmonics vibrational scientist and why I asked the questions I did when I began trying to understand harmonics, tuners, and how they work. Your experience is interesting to me because you have both the steel weight type tuners, and the one (the PDT) that is supposed to offer a combination of dampening and changing how the nodes behave. Could just be that the weight component of the equations is the more controlling factor than the impact of the dampening technology on the outcome. Its one reason testing the Sorbothane seems interesting to me too.