Not all fighters age the same. Unlike other Chute Box guys, Anderson had good head movement and was able to evade strikers well. Most others were brawlers who took a lot of damage. Anderson still had great reflexes when he fought Forrest. He was around 34-35 then. But he clearly had declined some by the time he fought Weidman at age 38, in terms of reflexes and chin.
I'd say current 30-year old DDP vs. Anderson between the ages of 31-34 would be an ideal fight. As I've noted already in the threat, Hendo was somewhat comparable to DDP. He probably hit even harder, though his striking was less diverse. He'd just gone 5 competitive rounds vs. Rampage for the LHW belt before facing Silva. Though he didn't wrestle much, he was capable of it and had a strong clinch, probably from being an Olympic-level Greco wrestler in his early 20s. In fact, some of his training partners said he was the strongest guy they knew. He also had an iron chin and was durable.