Brad Richards is not as good as Backlund at this point. He was a Conn Smythe winner in the same way the Lecavalier was a Richard winner (okay, he's not as bad as the cav, but he's a shadow of what he was). Does he put up more points? Sure. Is he playing on a way better team, with way better linemates? Yes. Also, other notable 2nd line stand-ins for the Hawks include Michal "why is he still playing" Handzus.
Your point about the strength of the Hawks as an overall team is notable, though. That aspect of the team is a rarity. However, I'd liken Backlund to Hanzal (minus a few inches): amazing defensively, not mind-blowing offensive numbers, but still able in the offensive zone. Would you take Hanzal as your 2nd line C? I'm sure most teams would be okay with it.