Idk if Gassiev can find a way to reach Wilder due to length before the dynamite straight right from Wilder finds him.
I agree with you. Usyk's defense is a bit porous, and punches from most of his recent opponents have been getting through with a bit of frequency. At the heavyweight level, that spells KO, against a power puncher. At this juncture, I'd say Wilder KO's Usyk. Gassiev on the other hand showed an airtight defense against Dorticos, and the shots that did land on him, he took fairly well. Not saying he would be able to take Wilder's power, but his defense is definitely tighter than Usyk's is. I could see him getting outpointed, instead of KO'd. Due to the increase in size, power, and reach disadvantages Gassiev would face moving from Dorticos, and Usyk to Wilder, I'm not sure that would be a hill he could climb and make it to the top, but I definitely see him being a tougher nut to crack than Usyk, vs Wilder.
Since Usyk left James Ali Bashir he tries to change his style to more aggressive one. Against Glowacky he was hardly hit with one decent punch in 12 rounds, but after becoming munch more aggressive fighter he gets hit much more often than before. If he comes back to his old Anatoly Lomachenko/James Ali Bashir style, he won't get hit as much. I think he will, because he is a smart guy and should understand that it's better to be labeled as 'boring' fighter than be knocked out.
I think Wilder it too long and too fast for Gassiev. Ortiz had more power and better skills than Gassiev and still failed to beat Wilder. Gassiev is much younger and has much better stamina though.