Following in the footsteps of Canard, I'll suggest some tweaks/new sets I think should be added.

Goodra-Hisui @ Leftovers
Ability: Sap Sipper
Tera Type: Fairy/Ghost/Bug
EVs: 252 HP / 4 Def / 252 SpD
Careful/Sassy Nature
- Protect
- Knock Off
- Earthquake
- Heavy Slam/Draco Meteor/Dragon Tail/Flash Cannon
The finer details can be ironed out later like the specific evs (some people run a bit of speed) and what moves should be on there, but specially defensive hoodra should absolutely be a set for hoodra. I would say its probably its best set rn, though specs is still very good. It takes advantage of hoodra's massive special defense stat in order to spread knock off and be a suprisingly difficult pokemon to switch in to due its wide coverage. Its able to leverage protect+wish passing to keep itself healthy over the course of a game.

Gyarados @ Chesto Berry
Ability: Moxie
Tera Type: Flying/Ground
EVs: 176 HP / 96 Atk / 24 Def / 212 Spe
Adamant Nature
- Dragon Dance
- Waterfall
- Tera Blast/Earthquake
- Rest
Specific evs can be adjusted (60 HP/252+ Attack/196 speed is a simpler spread), but resto chesto should at the very least be an OO mention. I do think that it should be its own set, as it is something you see a lot in tourneys, but it can set up multiple times in order to try and sweep the opposing team.

Ninetales @ Heat Rock
Ability: Drought
Tera Type: Ghost
EVs: 248 HP / 8 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Encore
- Healing Wish
- Flamethrower/Weather Ball
- Will-O-Wisp/Solar Beam/Scorching Sands
Since every other weather setter has a set (besides its alolan counterpart, but that is something that is yet to be reserved), I think its time to complete it by including ninetales. Max HP means ninetales can switch in as often as possible to set up the sun, with max speed helping it use its good speed to use its support moves. Encore can let ninetales stop setup sweepers and give its sun teammates free setup, healing wish can give teammates another chance to sweep. Flamethrower is more consistent, while weather ball has higher damage output (also the burn chance is something that has come into play during matches). Will-o-Wisp can cripple physical attackers to give teammates more setup opportunities, Solar Beam can hit Water Types for big damage and scorching sands can spread burn while hitting pokemon such as volcanion and armarouge for good damage. Tera Ghost acts as an emergency spinblock while letting it avoid big fighting moves.

Roar should be on volcanion in the OO section. I used it on my Volcanion semi-stall
here, but its been a good option for a while. It allows it to phaze out pokemon such as suicune or setup sweepers by tanking a hit and then phazing them, while also being great on spikestack teams. Its a genuine option that has been seen in tournaments I believe.