Interesting - especially as you have a 530. I was recently in a colleague's previous shape 525d Sport, and I was staggered by how good the ride was - it was almost magic carpet like. It was probably on the best tyres (Michelin Primacy's) but, especially for a Sport, I was just amazed. Gutted, in fact!
My car (C270 Avantgarde Estate) almost feels like it has no suspension. It's markedly better now it's on Michelins than the original Bridgestones, but even on 16" wheels with reasonable profile tyres it still transmits every tiny road imperfection into the cabin. I swerve around bumps I can see, and brace myself if I can't swerve.
It hasn't got Sport suspension and I understand that on C Class all versions (Classic, Elegance and Avantgarde) have the same suspension. Maybe the estate is very different to the saloon??