Imo, they were trash when they were brand new. I know that's not what you wanted to hear, but don't feel too bad, I think Yamahas and Kawasaki's of the era had much worse. I also realize you probably are not out there trying to shave down your lap times...
A couple things to consider...
1. I bet in 40 years of ownership you have had to change your front fork oil at least once, hopefully several times, or you have witnessed the rebuilding of a long neglected set of front forks...the smell alone should tell you..."Something Wrong!" Now realize that the rear shocks operate in a very similar fashion to the front forks...but they are not rebuildable.
2. Your rear shocks are an important part of being able to control your motorcycle safely, even if you just ride around "normally". Ever have difficulty cornering or braking on a bumpy surface? I know that you do, even if you don't realize it. This IS a safety issue, if you actually ride your bike. Sure, your shocks still bounce. I'm sure they always have and always will. The real question is how and when will they stop bouncing.