Does anyone have any experience or knowledge about on-car wheel balancing? Makes sense that it would take out any "rotating mass" vibrations that may not be related to an out-of-balance wheel/tire assembly. Looks like the biggest problem with on-car balancing is finding somebody who does it. From my Google searches, they seem to be popular with heavy trucks, etc. so they don't have to take the massive wheels off. The few reports I did find regarding passenger cars and "strobe" balancing seem to be very favorable however.

I used a strobe balancer in my younger days... 30+ years ago. I'm absolutely convinced it'* best way to balance tires. All rotating parts were "balanced"; axles, hubs rotors, etc.

You picked the car up until the tire was off the ground. A magnetic pick-up was attached between the floor and the lower control arm. Usding an electric drive motor, the tire was spun up to as much as 100mph. The sensor would detect when the "heavy" side was down and give you an approximate magnitude. The strobe would flash at "heavy". In the strobe light, the tire looked like it was standing still.

It'* probably different now. I don't know anyone who does it now.