I remember having denon volume issues with the 06 or 07 or 08 series. It was a differences in ramp speed with the avrs. I never got a good answer out of denon. That is about the time we signed up with integra. I do not remember more than one client who complained about it like you are. But I understand the frustration. Something as simple as a volume control should not be such a pita.
"When I eat, it is the food that is scared." - Ron Swanson