The DLC metagame is characterized by the most incredible support Pokemon we've ever seen. This will inform most of these nominations - at the top, you're either an
amazing support Pokemon, you're one of the few effective damage dealers, or you suck.
Support noms:
Blastoise -> 1
Blastoise was already a great Pokemon before the DLC drop and Flip Turn patched up its only weakness in staying on the field once Fake Out + FM wore out their usefulness. Completely controls the flow of the game and enables setup sweepers like nothing else. Definitely the best Pokemon in the tier.
Rillaboom -> 1
Rillaboom has an incredible toolbox of options that make it carry its weight each game. All of Fake Out, U-Turn, Grassy Glide, and Knock Off are wildly useful at about all stages in the game for shutting down the opponent's team (Grassy Glide being especially nice as a STAB move for slamming Blastoise), and it does a solid amount of damage with Grassy Terrain to where it's never a dead slot. Grassy Terrain helps you keep your team healthy and shut down Psychic Terrain teams. Very very splashable and always carries its weight.
Chansey -> 2
Chansey does the same Chansey shit as it always does, but now nothing deals damage. This is the time for Chansey to thrive. It is one of the only viable Stealth Rock setters, invaluable in a metagame where the top Pokemon have great pivot options, and after clicking SR, can usually just invalidate 4-5/6 of the opponent's team members. Teleport is a phenomenal 4th move that allows Chansey to escape the field once your opponent switches in one of the few Chansey checks in the tier and lets you bring in a favorable matchup, letting you rack up progress through Urshifu attacks, Stealth Rock, or general chip, vastly expanding the amount of teams that Chansey fits comfortably on (though Toxic is still pretty good for a late-game Chansey win condition).
Amoonguss -> 2
Amoonguss does Amoonguss stuff and now has access to Pollen Puff. Super irritating to play around with Knock Off being so prevalent and easy to click to deny Safety Goggles and is a viable way to shut down Chansey. The lack of Fake Out & inability to do damage can make it annoying to pivot into certain situations, which probably prevents it from being Tier 1.
Weezing-Galar -> 2
Definitely a bit of a jump, but absolutely deserved right now. Weezing provides one of the only checks to Urshifu & provides Toxic Spikes support which help break down the bulky pivots such as Rillaboom and Blastoise. Neutralizing Gas is as irritating as ever, preventing Rillaboom's priority STAB move & Chansey/Amoonguss' self-heal as they switch out, as well as protecting your team from the offensive threats of terrain / weather. All of these qualities are incredibly nice in enabling Chansey to do its thing, as its main check is resisted by Weezing and you're able to protect your team from TSpikes + set up your own to make faster progress.
Damage dealers:
Togekiss and Kommo-o are other damage dealers, but they're in tier 2 which seems appropriate.
Urshifu-Single-Strike -> 2
Urshifu forces progress like nothing else in the tier. There is nothing that can truly stomach a CB Wicked Blow outside of Weezing-G and Togekiss - not even Protect. Getting this in on a free switch, easier than ever due to the plethora of options the rest of the tier has, means that you're probably getting a kill or forcing damage on one of the only things that can check Urshifu later in the game. It acts as one of the only non-gimmick answers to Chansey and rips apart the slower, bulkier teams that it's usually found on. There is a very good case for this being tier 1, but I think I'm going to hold off on this one until the metagame develops more.
Volcarona -> 2
Heavy-Duty Boots are mandatory on Volcarona. That being said, Volcarona is one of the best damage dealers in the metagame. Spread moves are the best way to get around the omnipresent Blastoise and the Fire coverage it offers matches up quite nicely into the rest of the metagame with its Bug Buzz shredding Blastoise. It is also relatively easy to set up when the support Pokemon that deals the most damage in general is Rillaboom.
This is a recent tournament game that showcases Volcarona's lethality - even through Chansey, Blastoise, and Incineroar, Ezrael is quite easily able to win thanks to Volcarona's fantastic typing and Blastoise's support.
Urshifu-Rapid-Strike -> 3
Missing out on Amoonguss with its STAB coverage really sucks, and being weak to Grassy Glide really sucks. It's not bad, but I probably just wouldn't use it over Single Strike on the vast majority of teams.
EDIT: I originally nominated this to 4 but would rather see this at 3. Used Paraplegic's sample team and it has a really unique typing that allows it to capitalize on Volcarona, one of the scariest Pokemon in the tier. Sub's a cool set.
Noms down:
Gothitelle -> 2/3
Nothing deals damage, especially now that Melmetal's gone, and you can't capitalize on the offensive pressure that a partner provides to make up for its passivity. Also everything good gets a pivoting move which makes it significantly more difficult to set up Shadow Tag traps.
Incineroar -> 3
Incineroar has been incredibly unimpressive for a while now and this metagame has exacerbated its flaws. It faces direct competition for better support options in Blastoise and Rillaboom (it also underspeeds both of them, meaning it provides less effective Fake Out pressure) & its Intimidate is quite useless in a metagame where the most viable physical attacker either ignores Intimidate or just OHKOs it with Close Combat. There are better "crutch" Pokemon to just slap on your teams these days.
Dragapult -> 3
Dragapult was probably already a tier 3 Pokemon before the DLC drops and really struggles to deal damage against the extremely bulky metagame.
Excadrill -> 3
Excadrill's speed advantage is not super needed right now and it matches up incredibly poor into both Tier 1 Pokemon. Using Tyranitar also opens your team up to getting absolutely blown the fuck back by either Kommo-o or Urshifu.
Rotom-Wash -> 3
Doesn't deal enough damage and completely shut down by all of Rillaboom, Chansey and Kommo-o, as well as potentially facing competition from Blastoise as the Water-type on your team.
Milotic -> 5
Wicked Blow crits through Coils and OHKOs fast variants & faces direct competition from the much better Blastoise for the bulky Water type slot. I would not use this in the current metagame.
Conkeldurr -> UR
I'm not sure why this was on the VR in the first place but Trick Room sucks and just use Urshifu.
Bisharp -> UR
Intimidate utility is at an all time low - just use Urshifu.
Hydreigon -> UR
Doesn't deal enough damage and it's stuck with using Timid to outspeed Urshifu instead of actually forcing damage with its Draco Meteors. Being at -2 is really shitty in a metagame where everything can set up with a free turn or two.
Keldeo -> UR
Just use Urshifu Rapid Strike. Also Blastoise and Rillaboom exist.
Scrafty -> UR
Arctic edit: the pants lizard must be spared from the horrors of the viability rankings