I don't think the W201 rear suspension is any worse than that of the E36. And it's much more sophisticated than that of the E30.
The problem is you have a bunch of rubber bushings in the rear suspension, which tend to wear out and lead to sloppy/loose handling. In my case, this problem was even more pronounced, since I actually had cracks in the rear subframe: the whole thing was flexing under hard cornering. Now that the subframe has been repaired and all the bushings have been replaced, it's rock solid.
All in all, I think the suspension design is clearly better than the E30 and about equal to the E36.