I think you need to watch that fight again. Henderson never lands a clean punch at distance on Anderson's chin. That's not as much of a statement on Dan's inaccuracy as it is on Anderson's ability to make strikers miss when they are at the limits of their range, and he had significant reach on Henderson.
However, history has shown that Anderson does significantly less well against fighters when he does not have that reach/length advantage. It's overlooked by a lot of his fans, but that's the simple fact.
In the actual Forrest/Anderson era, Rumble was still a kid, still fighting at ww, and I think Anderson would have exposed his inexperience; but in 2 or 3 years, as Johnson grew into his body and they were both in the low 200s cageweight, I think it's 50/50 that Johnson catches Silva and knocks him out cleanly. If Johnson hadn't already virtually abandoned his grappling base by that point, the percentage would have shifted into his favor. I do not think Anderson ever possessed the power to knock out Anthony cleanly.
