I am passing this around in case others face the same issue:
I've had this issue for a few months on a relatively new pro-10 where prints were too dark (I have a calibrated workflow) and I could always compensate using some brightness boost in the Canon Print Studio plug in. My pro-10 was connected wirelessly.
Some folks were warning agains the airprint driver on Macs, that it was messing things up. I don't think I had that driver installed. I checked, rechecked, reinstalled, etc, and the driver chosen never said Airprint.
But then I decided to uninstall all versions of this printer and start from scratch with a USB cable connected, and bingo! this solved the problem. So there you go, I hope somebody finds this useful.
My only inconvenience is that now I need to have the printer next to the Mac, but I don't feel like wasting more time and debugging the wireless connection.... Oh well....
It's an awesome printer; I just did a big print on Canson rag photographique and it looks just gorgeous.
