while I think you are sorta right, I think both are still very valuable contributing players. I think you are a bit more right as far as Harris goes than peppers.
Harris' primary value is in his leadership ability and I don't think he has diminished in that role.
Peppers, though, really seems to be sorta rejuvinated by going to Chicago. He's done overall quite well from what I have heard. I think people around here forget that sometimes the impact a player has isn't felt on the stat line, and I do think (at least last year, haven't seen a ton of him this year) Peppers wasn't taking plays off and putting in effort to really change games.
If you go on Chicago's forum, they have been VERY disappointed with Pep. He was nowhere to be found in the Lions game.