New year, new noms.

A -> A+
A+ is pretty barren rn, so these are the main mons I think should rise.
Gking is gking, its an incredibly glue mon due to its ability to soft check so much in the tier while also pivoting and applying pressure, whether that be from status or from its litany of coverage moves. From its stabs, to ice beam and flamethrower, to even surf to beat heatran, its able to customise its moveset to an insane degree. Yes some mons abuse it, but it can at worst, become a pivot regen bot, which is not the worst thing in the world.
Screens are good, and pult is absolutely amazing into screens due to infiltrator bypassing them. But even in general, it feels like pult is just super good due to its fast speed and ability to utilise any set it wants. From status pivot, to specs, to band, to screens, just anything it can really do, and while they aren't always the standout mon on the team, it always pulls its weight. Checking stuff like zama and woger is just the icing on the cake.
I think if you want a successful offense team, then lando is a must have for your team. While taunt sets are very good, I think some experimentation truly pushes lando into the A+ rank. Smack down I've been using a decent amount which turns the metal birds, the status birds, and even potentially dnite from pokemon that can usually take it on into mere targets that have to run away from it. But other options like SD, scarf, rock tomb are also viable options that really diversify its gameplan and make it much more annoying to deal with. But the bread and butter of "get up rocks, check a physical attacker or two, then pivot" is frankly good as ever.

B -> B+
Maybe a bit of a personal pick, but I think volcanion is amazing in this meta. Firstly, it stuffs any and all molas, only av can even pray to beat it and they get heavily chipped between fire spin, and potentially taunt and/or sludge bomb poison. Its also a decent waterpon check with sludge bomb, as while it doesn't appreciate knock off, it can usually take one or two grass moves and ofc switch into ivy cudgel. It can also check stuff such as Gambit, Scor, Cinder, Pult, Hatt, i-val, Molt, Gking, Clefable, Primarina, Hamu, Moth, Scizor etc. It can also be decently flexible in its slots, both item wise and moveslot wise. Boots are good, shuca can trade exceedingly well, lefties gives it longevity, custap can be amazing into offense. Fire Spin can trap shit, with taunt helping that as well, sub can scout switches incredibly easily, Flame Charge is okay to make it faster and thus threatening against offense, Roar can phase out setup sweepers, Wisp can cripple stuff like Dnite more reliably etc. Just an incredibly flexible pokemon and it feels like most playstyles appreciate its talents, from HO to balance.

C- -> UR
Think these are kinda just bad and not really justifiable at all, as while they do have niches, they are way too small. Toxicroak is basically rain exclusive, which is not really a good start to begin with considering rain isn't great, but its not good at all. In theory, being a rilla, waterpon, zama, rai, hamu check sounds nice, but it kinda isn't worth it in actuality. Rillaboom does way too much to you, +2 wood hammer just completely annihilates you and hhp just wrecks you immensly (which has been seeing more use). Waterpon it does check, but it doesn't really stop it from clicking spikes on rain. Zama it does check well, but rain has other options like specs torn to check zama. Rai its only okay into due to ice beam chunking it, while hamu still sets up spikes on it. It also lets in pokemon such as ghold, pecha, gking which rain does not appreciate at all dealing with (particularly gking which resets weather). You can also use stuff like tusk or lando to check it pretty well despite toxic, and thus force it out (which rain teams don't like these mons since they can either do lots of damage or pivot respectively). And reminder, this is already on a niche playstyle.
IDT I've seen quagsire stall in a long time, unaware+spikes setter sounds cool but you take way too much damage from shit to jusitfy it most of the time. You kinda just are better off using dondozo 90% of the time or just a bunch of foul play mons.
Chansey is a similar case, it sounds cool but on stall typically blissey with an item is better (like lefties or cloak), while chansey offense is kinda a thing for the past. Doesn't see much use, and IDT its talents are as needed.

C -> C+/B-
Sz made a great rmt about it but TLDR, its defensive profile is insanely good and covers things that not much else can do while being a great breaker with its stabs+coverage. I'll just copy the part that sz talks about in his rmt:
Hydreigon Has Levitate + can function as a ghost resist + dragon type and fire off unresisted coverage with a very unique defensive utility of not only a fire/water/grass/ghost/dark resist + psychic immunity, but the special defensive utility that only one other viable ou mon can use (latios), a levitating steel, which provides a steel type with a ground immune, effectively walling + immediately forcing out threats like substitute kyurem, gliscor, landorus therian, Clodsire, Ting Lu, etc.
Feels better then all the C tier stuff, so should prob rise. More confident on C+ ranking, but B- is also something I wouldn't argue with.

B+ -> B
I’ve tried to be positive with this mon and have given it a spin several times, but it is just so clunky to use in a lot of match ups. Its very defensively awkward where there are SOME match ups it’s quite good into, but it’s also a Dark type that doesn’t really check Dragapult or Gholdengo comfortably by itself when the former clicks U-Turn or Dragon Darts (or wisp!) and the latter is capable of just blowing up most Ttar with +2 MiRs and FBs. This forces teams to have to fit extra back up for these mons which isn’t desirable in a tier with so many powerful and demanding threats. It’s still possible to do this and support Ttar but the teams that can are limited. Its lack of longevity is exposed through how easily it’s worn down by even lighter hits alongside hazards and its poor speed makes it very easy to exploit or just blow back. And with how weakness laden its typing naturally is, it also doesn’t really check that much in practice. Yes CB is threatening
when it predicts well but with a Pokémon that’s so vulnerable if you click the wrong move, that’s not great. And yes sand+knock is neat for helping against more resilient mons that tend to blanket check stuff, it’s not enough alone to keep this in B+ when its flaws are what they are.
I think a lot of this nom is kinda just, unfair to ttar. While the gholdengo point is valid (though fitting ghold checks isn't too hard), none of the darks appreciate pult clicking u-turn or wisp, and d-darts also chunks any non ting or gambit dark (hamu, rai, weavile etc). While it does have limited longevity, its bulk is more then enough for the BO teams or offense teams that ttar finds it on, as taking one or two powerful hits is more then enough.
It also checks a good chunk of pokemon more then you say. Darkrai (non focus blast withstanding, but even ting doesn't like taking +2 focus blast), kyurem, pecharunt, deoxys-s, pult, garg, i-val, molt, raging bolt, gking, torn, zapdos, ceruledge (unless its CC but that is rare nowadays), glimmora, heatran, iron moth, latios, goltres. Thats a good chunk of pokemon that it can help handle. It doesn't deal with all their variants, but it can help stave them off pretty well. CB is threatening primarily because even resists don't like losing their item, and the few that do absolutely despise taking stone edge (that being gliscor, clefable and corviknight). Your primary goal is to click knock off, and then maybe click coverage if needed. I also think you are heavily underrating how useful sand is. Ignoring that it enables excadrill, it also:
Breaks dragonite multiscale
Stops pokemon like waterpon and clefable from recovering as much health
Cancels out lefties on zama and rilla (g-terrain but same difference)
Boosts the spdef of garg as a teammate
Cancels out sun completely
This is utility that you get just by ttar existing. Combine that with the usual utility its other moves give (knock removing items, rocks are rocks, t-wave to slow down mons, roar to phase out setup sweepers), and you have something that can check a bunch of pokemon