I couldn't agree more with the Kartana and Tornadus rises, Kartana excels as a cleaner and a wallbreaker while also can offers utility to HO running defog and Tornadus brings to balance teams a good speed tier while also checks many things that threaten balance such as SD Kartana.
I can't say nothing new about those two, I glad that they are receiving the acknowledgement that they deserves in the current meta.
Also I would like to make this nomination
-->B-
I know that Araquanid is in the C rank because is mostly a niche mon but I think that it's not only the best SW setter in the meta it's also can work as a decent wallbreaker.
Shuckle and Araquanid are in the same rank but in my opinion Araquanid outclasses Shuckle in the current meta. Yes, Shuckle has SR, better bulk, Knock off, encore and it doesn't have to risk nothing in 50/50 situations with Magic coat but its passivity is something that can be really bad for your team in the current meta, many of the set up sweepers in the tier that can use Shuckle as set up fodder are the z move users that doesn't care much about knock off or encore, so outside of just using a slot in your team for SR and SW, Shuckle has more drawbacks as the SW setter like being dead weight against stall teams.
In the other hand, Araquanid offers offensive presence that the opponent has to take in count while also its typing, bulk and ability allows it to check many threats in the tier such Ash Gren, Volcarona, Heatran, non dragon move Zygarde, defensive Landorus, Mega Swampert, Keldeo, Charizard Y and Gliscor. Also only a few mons can use it as set up fodder like Dragonite while others take enough damage to be revenge killed by other mons in the team if they try to set up in front Araquanid.
Araquanid also helps against Trick Room teams, it's slower than some TR staples like Magearna, Crawdaunt and Marowak, helping a lot to its teammates in a such desfavorable matchup.
And the last thing that I think that make Araquanid worth of a higher rank is its ability to pass through the most walls or at least keeping them low for its teammates and doesn't allows wish pass in the mid game like Shuckle does.
In the first instance, it can seems like a joke, but metronome Araquanid is a really good wallbreaker, the things that can OHKO Araquanid can't switch in for free and neither can't be bring to the field with slow volt turn because Araquanid is even slower than min speed Magearna.
Usually the defoggers or water resist such Toxapex are the switch ins to Araquanid, once they are in, Araquanid can pressure them spamming Liquidation and once the opponent realizes that Araquanid has metronome, it is forced to sacrifice something if the wall doesn't has nothing to beat it before fall (like Toxapex without toxic or Mew with only ice beam) and the ones that can beat it such defensive Zapdos are forced to stay with low hp or don't defog, in any of the both cases, its teammates would appreciate it a lot.
Maybe I don't explained the reasons of why I think that Araquanid is better than c+ in the best way, so I'll put two replays where Araquanid was the MVP.
vs another SW team with dual screens support:
https://replay.pokemonshowdown.com/gen7ou-692949659
Here Araquanid saved the game of a boosted Zygarde taking a hit and weakened it enough to be in range of my own priority move, avoided the set up of the light screen, set up the SW and saved the game again weakening a Mega Tyranitar enough to be revenge killed by Diance, and it could have been the same story with Victini, Diance also take a +5 stored power and revenge kill a +1 Victini with earth power after rocks and Liquidation.
vs stall:
https://replay.pokemonshowdown.com/gen7ou-693160895
Here SW was useless but Araquanid wasn't, Araquanid weakened two mons for the Kartana sweep and forced my opponent to lose its mega to rocks just to break the metronome chain, if my opponent had not sacrifice Sableye and Araquanid would have not got para, Zapdos would have got KO by Liquidation after rocks.
These wasn't the best games that Araquanid have had but I didn't save the others game where Araquanid was even better but I think that these show how good is Araquanid like support and wallbreaker, maybe not the best but it's a solid mon in the current meta.