VR updates!
Now that the metagame has had about a month to settle itself, there's more room for clearly defined tiers. As a result, we now have a tier 4! I've enlisted the help of
Yellow Paint to assist in the initial VR revisions, but please feel free to nominate suggestions to the viability rankings; we're still very early in the DUbers' metagame.
Changes to tier 1:

Necrozma-Dusk-Mane (2 -> 1)
The Weakness Policy set has shown to be metagame-defining; both Sunsteel Strike and Earthquake provide great coverage and defense boosts as max moves, and it functions well both in Trick Room and as an independent attacker with Dragon Dance.

Lunala (2 -> 1)
Lunala has many similar traits to Dusk Mane, with a plethora of power and the ability to function well in and out of Trick Room. It can do Weakness Policy in tandem with its absurd bulk from Shadow Shield, run Calm Mind as an alternative means of setting up, or run Colbur Berry to nearly guarantee a Trick Room.
Changes to tier 2:

Blastoise (UR -> 2)
Blastoise boasts a unique role in being both a Steel and Fire-type resistance with Follow Me and Fake Out, two very useful moves to support other Ubers. Yawn is great at forcing difficult choices with opposing Dynamax, and it gets additional phenomenal support moves in Haze and Life Dew. While more niche, a Shell Smash Water Spout set can also be decent, as few Pokemon resists Water in the tier.

Indeedee-F (3 -> 2)
Indeedee walls Lunala completely with Follow Me, which is a huge deal. Psychic Terrain blocks Fake Out and other priority attacks, and is unlikely to be reset without an unusual choice in Dynamaxed attacks. It's a great assist for setting Trick Room and Helping Hand.
Changes to tier 3:

Eternatus (2 -> 3)
Dynamax Cannon doesn't hit for impressive damage on most non-Dragon Dynamax targets. It carries a lot of shared weaknesses without a lot of independent strengths. Its moves simply aren't strong enough. Its speed is still impressive, though, and it can trade with a good number of Pokemon in the tiers above it.

Gyarados (UR -> 3)
Gyarados would be significantly better if it could outspeed Zacian at +1; still, it resists Behemoth Blade, so it can be a potent Dynamax sweeper with a set of Waterfall / Bounce / Earthquake / Dragon Dance. If Gyarados snowballs and gives threatening allies Speed boosts with Max Bounce, the game can be all but over.

Jirachi (2 -> 3)
Being weak to both Fire- and Ghost-type attacks leaves Jirachi open to a lot of shared weaknesses with partners it's trying to redirect attacks away from. Tons of Pokemon threaten it, and both Blastoise and Indeedee offer similar roles with Follow Me with better typings for most team compositions.

Kyurem-White (2 -> 3)
Very, very strong, but tends to be Dynamax-reliant and that is not good when Dusk Mane and Zacian are running around. Requires Tailwind and frankly Dynamax to be effective.

Milotic (UR -> 3)
Similar to Blastoise in being able to sleep Steel-types effectively, this time with Coil + Hypnosis. Its damage is very underwhelming, but it does also discourage Incineroar from switching in frequently. Teams without powerful special attackers will have trouble breaking Milotic if it can get going.
Tier 4:
The following Pokemon were moved down from tier 3 to more appropriately represent their power level:

Zamazenta (3 -> 4)

Whimsicott (3 -> 4)

Rhyperior (3 -> 4)

Gothitelle (3 -> 4)

Tyranitar (3 -> 4)

Venusaur (3 -> 4)

Dusclops (3 -> 4)

Ditto (3 -> 4)

Excadrill (3 -> 4)
New additions:

Grimmsnarl (UR -> 4)
Grimmsnarl can set up screens quickly to reduce the impact of the opponent's damage quickly. However, its usefulness ends beyond screens if the opponent has Indeedee, and it must choose between 8 turn screens with Light Clay and surviving an attack from a Steel-type with a Focus Sash.

Dracovish (UR -> 4)
There are few good Water-type resists in the tier, and with Speed control, Dracovish can pressure lots of damage on various targets. Choice Scarf Dracovish fails to outpace Zacian, and it's not quite slow enough to do Trick Room things, but if it can whack Dusk Mane with a boosted Fishious Rend, it will hurt.

Hitmontop (UR -> 4)
Hitmontop is a fair alternative to Incineroar, boasting Sucker Punch for ease of triggering an ally's Weakness Policy, as well as Wide Guard to handle any Heat Wave being thrown in the way of Zacian and co.

Gastrodon (UR -> 4)
Very few Pokemon resist Ground in the tier, and after a Stockpile, Gastrodon can potentially be difficult to KO, spreading Yawn to further annoy the opponent.
Pokemon that have been dropped to UR:

Zamazenta-Crowned
It tries to be a happy medium between regular Zamazenta and Zacian-Crowned and fails miserably at both.

Dragapult
Marshadow is a better fast Ghost and doesn't rely on Dynamax to be effective.

Jellicent
Awful. I initially thought this could be OK as a TR setter that could spread Will-o-Wisp and Strength Sap but yeah it's awful.

Lapras
If you want screens that badly, use regular Zamazenta or Grimmsnarl. Using up your Dynamax for a very weak Pokemon offensively by DUbers standards is hard to justify.

Kyurem-B
Dragon Dance and Icicle Spear don't change the fact that this mon gets completely bodied by the Steel-types. Awful.

Melmetal
Much better Steel-types are available.

Terrakion
Beat Up cheese is very dangerous in a metagame with Sash Marshadow; if it doesn't get Beat Up (with the wide selection of Follow Me users in the tier, very possible) it is utterly demolished by the majority of the tier, including but not limited to the Steel-types.

Togekiss
Fairy-type redirection doesn't really help when the attacks you're redirecting are Behemoth Blade and Sunsteel Strike. Does nothing Blastoise can't do, since you're definitely not maxing Togekiss here.