MC 8.3 now offers different color space views of the source/record monitor and one of them takes "video 16-235 (8 bit terms) and scales it to 0-255 as one of the settings. You can also look to source settings when AMA linking to the files and go to to the color tab and there you can manipulate the range or add a LUT to get proper display.
Another variable in all of this is that QuickTime X is not the best tool to judge by as it tries to make things look good rather than correct and will do its own manipulation of color. There are many many threads that speak to the QuickTime gamma issues out on the Internet.
Ultimately, MC is a Rec709 editing system at heart (slowly changing) so a properly calibrated HD monitor with I/O is going to be your real viewing canvas (not to mention scopes).
How does this same file compare when opened in Resolve?
On that source settings page, if I select the "gfx-video level" drop down menu and choose "expand video levels to graphic levels", the files look like the originals. But if I export from there the blacks are too black. If I export the files with the milky blacks, without changing any source settings they look normal in the final file. The same files look fine all the way through in FCP7 and PP.