I agree with most of what you're saying, but I think I disagree with your main point.
If we're comparing apples to apples, Norman playing on the outside vs Captain playing on the outside, as bad as he was at it Norman was still better than Captain. Captain was the worst starting CB I've ever seen in a Panthers uniform, and that's including Norman. Norman hasn't really spent much time in the Nickel, so we can't really compare their performance there. But Capt was a good Nickel.
in 2011, a year where captain started on the outside in all the games but one, he gave up the 4th highest QB rating when thrown at in the league. it's just a fact that when he's lined up on number one receivers, particularly big ones, he gets picked on.