I guess the loaded roller adds some realism but on-the-car balancing accounts for brake rotor, hub, etc.

 

hub and brake rotor should not effect the balance. Hub is to close to the axis, and rotor is balance at manufacturing. Chronic vibration is not a balance issue, its a suspension issue. Once the vibes start it degrades the suspension/steering parts dramatically faster. Yes the balance may creep a bit as the tires wear and stick on magnets fling off. Continuing to drive it like this just kills the rest of the suspension and rebalanceing the wheels is not addressing the damage done.
This is basic chassis service, no inherent flaw, no magic.

 

Maybe they shouldn't since they are at a low radius. I've never tried the loaded roller-type of balancing so I can't say on-the-car definitely better. It works for me and it might be worth trying if it is available.

 

I had a similar problem and mine was the struts, they were also leaking fluid.

 

Have you checked your drive shafts? Both of my 944 where shaken a different speed, and both times, I had a bad drive shaft. And both times, I had to break a the drive shaft on the street to find out where was the problem : )
But after changing or repairing, everything came back to normal.

 

oups, I've just noticed that this was a 4 page thread. Sorry