One other area that a typical MB tech might not look for on your car could be inner CV joints. As a rear wheel drive kinda guy I was amazed when I first saw the vibrations that can occur in a straight line due to loose CVs under load.
Since we have absolutely no 4matics in Florida I can't say how this will affect a MB. If the CVs were a factor the vibration would occur only under some form of loading.
Bosch Master, ASE Master, L1
33 years MB technician