In the toughness department the Diaz brothers were always slightly behind people like Edgar, Big Nog, Diego, Bisping, Gaethje, Lytle and Wanderlei
They belong in the category of super tough but still capable of being mentaly broken in a fight like GSP, Rory, Leben, Rampage and Griffin
They're mentally tougher than guys like Conor, BJ, Overeem that sometimes crumble horribly when facing adversity
And far tougher than guys like Woodley, Chael, Rumble and Vitor that always crumble when facing adversity
Nah he was up there with the first group. Watch his classic war with Paul Daley. He took a hell of an ass whooping at the start of the fight, survived and came back to get a TKO win.