Among the godfathers of MMA we should think of Jon Bluming, too. He was an excellent judoka and a student of master Oyama (kyokushin).
Plenty of written, official reports for Figg's fights and opponents fights, in other words there is proof that he could fight. To a lesser extent same for Dioxippus, which is an interesting man to bring up in a thread were people claim bruce "invented" something Dioxippus had mastered some 2000 years ago.