If Benson was still fighting B-level fighters, he'd still be running clinics on them and trashing them fight after fight.
Instead, he's facing the best fighters in the world, and unfortunately he just doesn't have the finishing weapons of someone like Pettis, and he's not recklessly aggressive like a Diaz.
He's still an offensive-minded fighter, and he tries to finish, but the weapons just aren't there, no matter how skilled he is.
He also almost stopped Diaz, and beat Jim Miller and Mark Bocek half to death, which aren't easy tasks.