I've said it before and I'll say it again: It may have been a good decision at the time in terms of the financial benefits, but spending four years of his physical prime wreaking havoc on his body in the WWF was the worst decision Ken ever made in regards to his MMA career.
However, like you said: He did have a pretty good showing in PRIDE. If I had to pinpoint a certain time, I'd say it was somewhere between his first fight with Tito and his fight with Kimo. Yes, he beat Kimo and looked pretty good doing it, but his speed and reflexes weren't as good (watch Kimo pop Ken with that double-jab at the beginning) and they just continued to get worse. Against Rich, we saw that he wasn't able to take a punch as well, which was only further evidenced in his subseqeunt fights against Sakuraba, Tito twice, and most recently, Buzz Berry. Now he looks slow and old. . .which is exactly what he is.
It's unfortunate, but not everybody can be Randy Couture.
When compared to fighting guys like Severn and Kimo, who had 80 and 90 pounds on him, yes, Ken's 25 pound weight advantage on Royce wasn't that big of a deal (and think whatever you want, but just know Ken had no more than 25 pounds on Royce).
And yes, 36 minutes is a long time, but Royce and his family were all pissed that they were stood up and pissed that the fight was stopped. Remember Royce's quote going into his fight with Hughes?
"Give me time and I will submit you."
He should consider himself lucky that BJM stopped the fight, because Ken was still fresh while he was a bloody mess and couldn't walk without the help of his family.
You're not going to get any disagreement from me.
I could've sworn I read about him training BJJ.