Tank did have devastating GNP as seen in his win over Hugo Duarte, who was a very good grappler.
Tank would have done that if he could against Frye and Taktarov but they were better grapplers than him. Frye was an early guy that had great GNP. So did Shamrock.
Mark Coleman was a whole different level. We are talking about an Olympic wrestler who also placed 2nd in the World Championships. Coleman probably had the strongest double leg takedown in MMA history and was the best or one of the best at holding people down. It's not fair to compare anyone to Coleman because he is still the gold standard for takedowns, keeping people down, GNP. Coleman only lost to Pete Williams and Mo Smith because those were like 20 to 30 minute fights. Had they been 3 5 minute rounds Coleman probably would have rode them out for easy decisions.