Looking at all this data you have collected sp00n, the what I am seeing is that the percentage chance to proc Berzerking and Mongoose is calculated by the game using your *base* weapon speed, and not the hasted speed.
As an example, look at the observed PPM for Berzerking in
This post. You had very little haste gear on, and you observed a "PPM with Hasted Speed" of 1.0128, which is outside of the confidence intervals calculated by your most recent data (assuming PPM is off of Hasted Speed).
However, all of the data you have collected falls cleanly into the "PPM with Base Speed" confidence intervals, so that would seem to indicate that the PPM calculations for Berzerking at least (and most likely Mongoose, as it appears to be the same) should be done using the Base Weapon speed, and not the Hasted Speed.
I'm still not sure how this relates to DMM's initial findings about different PPM values from different training dummies, although you don't seem to be seeing that effect, all of your data is consistent across both the 83 Heroic Dummy and the 60 Dummy.
I'm not sure if it is needed, but it might be useful to have a similar sized set of proc data on the same level 60 dummy but with very little haste gear on, just to really verify that the PPM is calculated off of base speed and not hasted speed.