I have had tires that are worn funny and become out of round (not flat spotted but more bulged). The wheels were perfect but a tire had a problem and ended up slightly out of round and unless you look for it closely you wouldn't even see it. Some people dont even look at the tire as it is spinning to see if it is out of round. A road force balancer can correct for a tire that is slightly out of round but if it is really bad it won't take all of it out.

 

When your tire/wheels are on the balance machine you could easily see if the tire has an issue. (bounce or wobble) That's if they bothered to look of course. If you've had your car to the dealership things like wheel bearings should have been checked....it's easy! Here's a balance machines need to be calibrated periodically and that could be the problem. Find another tire shop and have your tires balanced and ask them check the tires when it's at speed. You'll probably find what was causing your wheel shudder/shake....Gary