I don't think Weavile should drop. With the soaring popularity of Landorus-t and offensive builds in general which rely on Landorus-t as their catch all physical tank, Weavile gets a free kill easily vs those types of teams. Sure, some teams have some "switch ins" on paper such as Azumarill, Keldeo, and Clefable, but if you've ever played a game against it or even watched a replay you know those things aren't enough to last in the long run. They definitely also don't want their items knocked off, especially in the case of Clefable, where it losing its leftovers is pretty essential to its success. I'd even go for as to say that any team not using a Mega Scizor is somewhat Weavile weak. The popularity of psychics in the metagame is great for it. Weavile also has a new role now as a pursuiter which can trap and kill any Hoopa-U locked to a resisted/immune attack which is definitely a plus on most teams. It's also great to see people experimenting with Choice Band on it, as that hits really hard (2HKOes Clefable ffs) and has the added benefit of not chipping your health down to the point where a bisharp sucker punch can kill you after SR or something. It's definitely a massive force still to be reckoned with and should stay A+ imo.
I don't think Landorus-t should raise to S rank either. This is a similar boat to the scenario with Garchomp a couple of months back when it was by far the #1 most used Pokemon and people were nominating that for S rank too but it never went through. Usage does not correlate with viability, even though that may be assumed at first since the three S rank Pokemon atm (Clefable, Keldeo, Tornadus-T) are all used frequently in high level play. The main reason why Landorus-T has kept consistent #1 use recently is because of its just so effortlessly easy to splash onto teams: it's a defensive ground with Intimidate who can set up SR and gain momentum, and is immune to ground, and can check a bunch of top tier threats such as Charizard-X and Lopunny. The thing that separates Landorus-t is that Landorus-T by itself is not that big of a threat. I don't think anyone here has looked at team preview and saw a Landorus-T and just thought, "man Landorus-T is going to be so hard to deal with, let's see how I'm going to manage to take it down". It's not like Keldeo which can slowly weaken your team apart and you have to systematically think what Pokemon you're forced to sac to it, or like Tornadus-T where you're constantly struggling to kill it while it just tanks and pivots into your attacks all day while chipping your health down little by little until you eventually give. When you're dealing with Clefable, not only do you have to deal with it walling a bunch of your Pokemon, you also have to think about how you can't give it free turns to fire off thunder waves and boost up to be virtually unkillable in the late game.
Landorus-T is very easy to fit onto teams, yet it's also so easy to take advantage of, and your opponent can just use your Landorus-T to put immense pressure on your team. It's insanely easy to just double switch from Excadrill to bait a Landorus-T switch in into something like Manaphy, Kyurem-b, Keldeo, LO Starmie, Weavile, etc and then the Landorus-T user is at a huge advantage because these types of Pokemon naturally already have so few switch ins. It's also pretty easy to wear down, since it's constantly switching into SR continuously. Unlike other top tier pivots such as Rotom-W or Tornadus-T or U-Turn Mega Scizor, Landorus-T has no means of recovery, even natural recovery, so your opponent can just continuously weaken it until it dies. Some of the Pokemon Landorus-T typically switches into, such as Talonflame, Hippowdon, Charizard-X, Garchomp, can all just status your Landorus-T on the switch in with burn or poison and it'll just be severely crippled afterwards. Landorus-T is a very useful and splashable Pokemon in the tier, but its only used that much for its ability to blanket check a bunch of Pokemon instead of being the big threat itself, while also being easy to wear down since it has no recovery or means to regenerate HP making it very prone to status, and just falls to countless dangerous threats in the metagame.
Hoopa-U should raise back to S rank. What else is there to talk about besides the deadly Choice Band set and the newly discovered and just as devastating Choice Specs set? These two sets are arguably the best sets for it to run atm as they both hit incredibly hard, to the point where even your "resists" take half their health from just one hit and it's much harder to wear down Hoopa-U since it's not taking LO damage anymore. Whats more, is that Hoopa-U has the offensive typing, and both the physical and special movepools to abuse these sets. There's quite literally, nothing in the game that can avoid a OHKO/2HKO from this thing, which isn't nearly the case for all the other powerful hard hitters in the tier such as Kyurem-b, Latios, Keldeo, Azumarill, Mega Heracross, Mega Medicham, Mega Gardevoir, etc. That alone should make it S-rank. Then you have to realize the ease in how it pairs so well with many common pivots such as Rotom-W/Tornadus-T so its not even relatively hard to get it in the battle for free as opposed to something like Weavile. It's also not nearly as deadweight as offense as many people like to exaggerate, since it just checks a bunch of things naturally by virtue of its special defense and power, such as Starmie, Manaphy, Latias, all the electrics, etc.
Quite literally the only thing preventing Hoopa-U from being outright "broken" is the fact that Pursuit exists and that the premier Pursuit users of that tier naturally resist/are immune to its STABs and so they can trap and kill you. But even then, NONE of the Pursuiters can switch in safely on it, so you either have to A) sac something and let it die first, or B) be a prediction god and go to Tyranitar on the Banded HSF or Bisharp on the Specs Psyshock which can easily be telegraphed.
Also, no, Chansey shouldn't rise. It's just so immensely easy to pressure with powerful shit like Bisharp/CB Tyranitar/Hoopa-U, so easy to wear down with double switches and pivots like Rotom-W which can burn it and then volt out forcing you to take hazard damage for nothing, and so easy to use as free set up bait for your ferro/skarm/SD Garchomp or whatever. Haven't you realized by now that all the top defensive Pokemon in the metagame right now have some way to alleviate their passiveness? Look at Slowbro which has scald/twave/regenerator/calm mind, amoongus which has natural healing so it can't be worn down and can switch into most of the waters in the tier and has spore/hp fire/foul play/clear smog, even Mega Latias which doesn't have access to leftovers recovery has Thunder Wave, Calm Mind, and an absurd SpAtk stat and movepool to not be completely shit while still walling a huge portion of the metagame. The only even somewhat decent option for Chansey to deal with this is just Thunder Wave but that's definitely not enough when you consider how many Pokemon are able to pressure Chansey and use it to set up freely.