Hendo has taken some bombs in his career but when MW Anderson Silva hit him with a flush head kick he was wobbled. Gus just kept walking.
"Soldiers! Don't give yourselves to brutes - men who despise you - enslave you - who regiment your lives - tell you what to do - what to think and what to feel!" - Charlie Chaplin, Comedian
No argument can be made for Gus having a better chin than Hendo and Shogun never had crazy KO power. He has enough power to hurt anyone but not enough to put you away with one shot, his killer instinct makes up for it.
also he never hit Gus like he hit Machida, nor is it possible for him to hit Gus like he hit Machida since Gus is much taller