I have been trying to come up with a way to peek inside Dusty to see how well it is working.  I had been thinking of ways to hide a camera in there, but this seemed like a doomed idea, either the camera will get hurt, or it will not capture the image, or just cause a disturbance in the air flow.  Finally I stumbled on this great video on reddit.  They had the bright idea to put a strong light behind the bucket to cause a shadow to be cast by the dust.

I only have an orange bucket, and nothing close to a strong light, but it finally hit me that I have a car and the headlights are really bright.  A quick setup in a dark garage and a box to line it all up and it worked great!

I was able to see the dust swirling in with and without my Thien baffle, and also using my diffuser.  The results with the straight outlet and diffuser were about the same.  The dust flowed in a nice swirl but if I plugged up the inlet I could see dust cavitating back up from the bottom and upon inspection I could see a hole was drilled in the center of the dust.  

Adding in the Thien baffle seems to have eliminated this cavitation, when blocking the inlet there is no evidence that the dirt in the bottom is being disturbed. And there is no hole in the center of the dirt either.  I'm changing my view of the Thien baffle, it is not just that it reduces the air speed at the edge of the baffle, I think it also provides a more direct route between the inlet and outlet when the vacuum is increased by restricting the inlet and that in turn keeps the air below the baffle smoother and reduces cavitation of the dust.

Next is to cut a new baffle that lacks the lip, and probably one more that is 1/2 the diameter to see if the lip is important and if the diameter is a big deal.  I also need to compare the straight and diffused outlet with the Thien baffle.  I tested with only the diffuser and noticed that there was a pile of dirt under the diffuser.  If  the diffuser is not effective then it would be better to remove it, it adds complication and material on printing and can be a pinch point where material can clog up the vacuum.