I understand that you can't measure speakers as accurately as you can measure electronics. However, I feel like you're being too pessimistic about the variance one has to expect with these measurements.
@napilopez put it very well when he
posted a comparison of the various measurements of the KH 80:
The bottom 3 measurements look very similar, only yours stands out. There is variance in the bottom 3 of course, but not nearly as much as you seem to suggest is "par for the course". This suggests the differences in your measurement can't be explained by random variance alone. Especially since the differences are relatively low-Q, i.e. they affect the overall trend of the response, it's not just local variations.
People here have suggested likely explanations for these differences. The drop in low bass likely comes from compression. The rise in the treble likely comes from measuring using the tweeter as the acoustical axis as opposed to the one that the manufacturer specifies (centred on the Neumann logo). Assuming these explanations are correct, these are very easy to fix: just re-measure at a lower level with the proper acoustical axis. Then, hopefully, you'll get a graph that matches the other 3, most of the "variance" will be gone, everyone will be happy, and doubts about your measurement process can be put to rest.
Quite frankly I'm a bit surprised that, in the case of electronics, you're more than willing to go to extreme lengths to investigate things like the ESS hump or to push the boundaries on 120 dB+ SINADs; but when it comes to doing speaker measurements with laboratory equipment that costs the price of a luxury car, you're willing to dismiss very suspicious, broad, low-Q frequency response anomalies as just "variance", even though measurements other people made don't show such variance.
Don't you want to know what your system is truly capable of? Why not try to extract its full potential instead of rushing through reviews? Why accept such "variance" from the most advanced, state-of-the-art, accurate speaker measurement system on this planet when there are clear signs such variance should not be there and can be explained in other ways?