He is easily better then Hernanes just because he is balanced CM who rarely makes mistakes, tho not much impact either but does the expected mid level routine stuff.
I know that he is better than Hernanes, but that means shit. And why the hell do we need a mid-level player? We really shouldn't care if we can't get anyone better, because signing another quality CM should be done before we sold Pogba. This one is on Beppe, he did great this summer, but he fucked up here.
Even though his name was thrown around for 2 years now in my eyes Witsel is a panic buy to some extent, because a player of his level should be nowhere near Juventus. I would take him 5 years ago when he had potential, but he went for the money, says a lot about him. And everybody hailing our scouting and how we follow players for several years, etc.; I am fairly certain that Witsel doesn't have neither personality nor skill to match our criteria (unless we significantly lowered it).