Man, wish I had your fork! My 5 month old Diamond must be one of the "stiff" ones. Feels like the air chamber is too short-- I'd like to pull out a couple nonexistent volume spacers and set high speed compression 2 turns below zero. It's been re-bled under warranty along with new seals and lube, and the various adjustment ranges pretty thoroughly explored.
Feels like it could be great, but something's holding it back. At 165lbs geared up, I can't bottom it at any pressure high enough to balance the OTT spring, i.e. over 75psi, which sounds more like a pressure we'd expect for an Onyx. That fork must have a lighter neg spring to run those lower pressures.
Is your Diamond from the Boost generation (140-170), or a non-boost (130 to 160 travel)? Maybe they changed something to get the 170 option, that had side-effects, or some other running change. I see a pretty bimodal distribution of comments in this thread. Either "best, smoothest bump absorption ever, now that I've figured out how to stop it bottoming out", or "Harsh, stiff, beats me up, and terrible on chunky stuff". Gotta be two very different forks.