I won't fully disagree about the QB's importance in the game today. Especially as others have said with it being a passing league now, full tilt.
About other positions and rating their importance, I think it boils down to skill of the player. Outside of the O-line and interior clogging DTs, if a player is amazing, they can transform a team or games. As great as Anthony Munoz was, Ogden and so on, I don't think they could have transformed a game. There are some DEs that are more harmful them helpful- look at all the "pass rush" specialists late career, vs. when they were younger. Dwight Freeney and Bruce Smith come to mind. However, people like L-Taylor, Rice, Jason Witten, Singletary, D.Brooks, Ed Reed, D-Sanders and Lott slayed for most of their careers. And all of them were able to take over IMO.
That all said, a weak line on either side will can still mess up a team, it's just more manageable due to the numbers of lineman and scheming, especially offensive IMO. Mark Schlereth has been honest in that he couldn't due a moving block or something on Denver during their peak, yet you would have never known that based on the results.
But I don't like ranking positions by importance at all. The O-line is the number #1 reason IMO why the Pats' offense sputtered in SB42 & 46, because the line couldn't stop the pressure well enough for Brady's skillset at that time.