I agree with haasman and offer these additional observations. The high pressure "deCarbon" shocks on Mercs typically maintain their design damping characteristics until end of life when they fail completely, but they usually go well over 100K miles. Failure is usually evidenced by a sudden loss of oil, which will be quite noticeable. The RF on my 190E failed at about 60K miles, and I replaced it with a Bilstein OE replacement that appeared identical to the OE shock, which was made by Bilstein. The only difference was that the top of the strut rod was torx rather than a metric hex.
Shocks are transient control devices. They offer a resisting force proportional to the velocity at which they are stroked. They normally do not have any affect on ride height, but deCarbon type shocks do have a small spring rate due to the high pressure gas charge. You should inspect the struts/shocks carefully for signs of leakage - not just a slight film, but a real leak. If they are not leaking, they are probably okay.
You should also find a road with a good mixture of bumps and dips and take it at a brisk speed. If the body does not pitch and wallow around the shocks are probably okay, and your issues are due to something other than the struts/shocks.