To be completely fair to CMC, Kamara is playing at best back in the league level right now, so the comparison is tough for CMC regardless, because Kamara is playing at an unprecedented level for a rookie. You don't expect this kind of production.
Having said that, I completely understand what you're saying, and don't understand why the only rebuttle is "Payton and Brees!!!". Kamara is forcing the most missed tackles in the league per touch and averaging the most YAContact. CMC is near the bottom of the league in both. Your OC doesn't affect that.