The problem is, Aerial Ace is the only reliable attack you get, Rufflet is choiced locked pretty much 95% of the time unless it is running a Bulk Up set which is entirely gimmicky imo or Life Orbed which is fine, but leads to losing to anything of a higher speed tier such as FastFoo running hjk or Stone Edge. I do see some usage over Doduo/Taillow/Fletchling being decent, but generally I would like the priority Acro, the sheer power of Doduo and its Knock Off utility, or Taillow's natural Speed and still great power combination. I do however see mid C or more likely C- being reasonable as Rufflet hits less hard than Daru but has a 100% accurate attack and is faster than Daru but with worse coverage and overall has much less of a niche than Daru.
Something else that 2HKOes literally everything, has more speed, and prio is Rattata. But it isn't ranked due to having little to no reason to run Rattata over Bunnelby or Aipom or maybe Eevee. Ultimately, this is at least half way true for Rufflet as well, though with other Birds instead of normal types.
Krabby actually doesn't hit hard enough to sweep until late game and after heavy support, but 9/10 times DD Corphish, Tirtouga, Omanyte, or even just Carvanha could have come in and swept already. I do believe it is ranked for its Scarfed set though, and the small niche of not being weak to Mach Punch making for some easier sweeps if you fail to remove Timburr.
How is this largely different than what you've been suggesting? SD sets can break PorySprit and can break Ferrosprit after Ferro has been weakened just a tad and then not be have to lose to Pawn afterwards if you are a BJ set. All ghosts struggle to revenge, it cannot be Trapped by Diglett, and it has flexibility in running pursuit to remove Gothita. Sword's typing also creates a very anti meta pokemon which overall gives it viable niches and a plethora of options to run. Honedge is fine where it is, and in fact I'm partial to a raise to B- after almost straight up losing to it so many times.
