I also agree with the rankings about Stingers. From a melee perspective Stingers aren't that great. Their range is terrible against melee and as a three man squad they quickly get overwhelmed by a bonding squads superiority in attacks. Sure you can add Deathreavers to the mix but usually Deathreavers/Any Range is a nightmare for most melee builds.
I agree with this, but stingers are among the nastiest options available to put behind the rat screen. The only options that can deliver more damage are Braxas, Nilfheim, Airborne, and the WTF squads, and those are all rated B+ or better in this scale.
And to look at this from the other side - I don't see why Q9 would be considered an A+ in these rankings if we're not taking into account the rat screen. Q9's offensive output is almost strictly lower than the stingers - he'd be better off with a range 6 triple attack of 3 than his special against melee squads. And his toughness is not that great when knights+gilbert or heavies+Grimnak start dropping attacks of 3 and 4 on him each turn. Granted, Q9 is a beast against melee when fronted by rats and backed by Raelin, but as you say, so is any range.
I've always considered Q9 more of a ranged figure counter than a melee figure counter, because Q9 by himself can take out waves upon waves of 4th or 10th.