I could easily put up with a bit of roll after putting it in park, but my clunk is so bad that it makes a pretty loud clunk when just applying power and releasing it while running at a steady speed. It is definitely not correct.
It might be interesting to know how much travel you have at the tread of the tire if you raise one rear wheel and turn it back and forth. I've got 3.5 inches on my 300d, and about 0.75 on my 240D, which I believe is nominal, or better, for a car with 250 kmiles. I found somewhere on the net where a guy said a quick check is to have less than 2 inches of slop at the tread, with 1 inch closer to nominal. He said that anything over 2 inches indicates a problem.
All of this assumes good flex disks, support bearing, etc.