Why insufficient? Patterson would be a combination of speed, power and talent that Dempsey never actually defeated in his own career. I'm not sure there's anyone Dempsey beat that Patterson wouldn't have beaten.
Floyd was not exactly a boxer .. Floyd was a swarmer throwing lighting combinations and using decent defense .. he was not a pump the jab and stick and move guy type fighter .. as far as Dempsey goes , you either think he was for real or you don't .. as much as I remained disappointed that Jack threw his prime away and that we never got to see the best of him I still believe in my gut that he was the real deal as far as talent and heart go .. when I watch the footage of the Toledo Dempsey in training and in that ring we are seeing what should have been a heavyweight version of Manny Paq .. my long winded point is that he would have cut through Patterson pretty fast .. Floyd could not take what Jack could dish out ..
Floyd was a slowish starter. He doesn't get out of round one with an opening stanza knockout specialist like this.
I don't think Floyd would be prepared for what Dempsey brought to the table. Dempsey was a hellacious puncher. Sharkey who was a larger fighter than Patterson stated "I never thought any fighter could hit that hard" regarding Dempseys power. And this was past prime Dempsey. I don't think Patterson lasts more than two rounds against the best Dempsey.
Did Dempsey ever go toe to toe with a skilled, lightning fast fighter with KO power in both hands? Firpo, among the most crude and skill-less heavyweight contenders ever, went toe to toe and almost KO'd him. I don't see why Floyd is such an underdog here. Because he got blasted out by Liston, a brute who would outweigh Dempsey by a good 25lbs? True he also got KO'd by Johansson, a hard puncher himself whom Floyd knocked out in two rematches, but then Dempsey was KO'd by Fireman Jim. Just saying.
The reason that Floyd is such an underdog is that he is not particularly elusive, and not particularly durable. Yes he has some very nice skills, but they are not the ones he needs. The bottom line is that many of Dempseys opponents, were either harder to catch or harder to stop. Yes Dempsey was stopped by Fireman Flynn, but even if we assume the fight to be on the level (not a given), it happened when Dempsey was a regional level fighter. It was also the last time that he was ever stopped. The obvious conclusion from this must be that he was an exceptionally hard fighter to stop, and that Pattersons punchers chance is a pretty slim one. You could argue that Patterson was unlucky to share an era with Liston, but I do not think that he was unlucky to share an era with Johansen. He is just the kind of fighter that you have to be able to beat to win the lineal title in most eras. I imagine that Dempsey would have made fairly quick work of him as well.
This fight matches one of the all time p4p hardest punchers against the champion who had perhaps the worst chin. You do the math and take it from there. Dempsey also had very fast hands, much faster than say....Ingo.