I'm not saying Feraligatr shouldn't be B-rank(let it stay there, it's not a bad mon as such). I'm simply using Gatr as evidence that Weavile should be B+ because it's a better sweeper. Feraligatr being B makes sense: in comparison, it's Weavile being B- that makes absolutely no sense.
Don't contradict yourself.With two water-types already, it's not viable to have another water-type, which is why Feraligatr should be C-Rank: rain teams have no space to run it as of now
Weavile has a niche as Pursuit trapper and an Ice Shard user, and is pretty much limited to that role, although it executes it solidly. However, on no planet in this universe is Weavile a better SD sweeper than Feraligatr. I challenge you to name something that it can set up on - basically everything relevant in OU can OHKO it or at least do enough damage to severely cripple it. Even once you have set up, Weavile isn't too great of a sweeper because it is easily checked by a large proportion of the tier, including most Scarf users and anything that it can't OHKO at +2. The calculations you've provided prove absolutely nothing since you've looked at two very specific examples, both of which are completely irrelevant to the discussion. If your main argument is that Weavile should be ranked higher because it is a better SD sweeper, I think you should consider trying out SD Weavile on the ladder for yourself and see how much success you can have with it, compare it with superior SD sweepers and see the difference.