totally agree with your conclusion, but if you have no idea where the cause of the problem is and rely on that the persons in the garage know what they do you end up in this "trial and error" and "process of eliminination" :-/ Meanwhile a young expert (very engaged, dedicated car technician...

Got exactly the same problem with wobbling / shaking starting at 60km/h, but only under load, uphill or when accelerating. Drive shafts front and rear exchanged, prop shaft exchanged, haldex unit exchanged (had other issues with worn out bearing). Test drive with removed prop shaft showed that...