The seals wouldn't have to be worn or loose enough to let water in to cause wind noise, especially at highway speeds. I had some bad windnoise and replace the rear passenger door seals and the driver's window, that's right the window. A previous owner had replaced the glass with non-Mercedes glass, it was not as thick and even though it fit, it was not quite right. Have a good look over the seals, doors, sunroof, and even the seals over the firewall and around the trunk. Also, outside the car on both sides of the windshield under the lips of metal that run up both sides of the front of the car there is rubber stripping that runs through there. A lot of wind finds its way into this area. Check those seals as well. My 420SEL is much more quiet than my old DeVille, and that was pretty quiet.
1995 E420 - retired
1986 420SEL - retired