I've seen Rose play good man defense in iso situations. He just sucks defending the pick and roll.
No. He lacks the lateral quickness to stay ahead of his man, and the focus to consistently be in correct position - both one-on-one, AND in rotations. And the reason he can't defend the pick and roll, is because he lacks both the awareness to see it coming, and the quickness to slide over, or recover.
Whatever you've seen this year, where he played "good man defense" -- is an aberration, and not the rule.
He's terrible. Stop it.