I was kinda hoping for screens/light clay first because that's going to be a camel back breaker for any sweeper whether its moon, volc, or even current OU ones since the perception of what can RK or kill it during the setup turns is going to be wildly influenced by throwing screens in the equation, especially with mono tera to alleviate duel weaknesses (moon's dual fairy weakness and volcarona's dual rock. A tera bug volc behind screens can muscle power gem heatran during the initial setup). Want to point out that in the scenario where these aren't unbanned and borderline screens gets a light clay hit we may want to revisit them
again which sounds unlikely/annoying to deal with.
I didn't see it mentioned in the initial post when talking about potential answers to volc, but one that immediately came to mind was
Skeledirge @ Heavy-Duty Boots
Ability: Unaware
EVs: 248 HP / 8 Def / 252 SpD
Tera Type: Fairy
Calm Nature
- Torch Song
- Roar
- Shadow Ball
- Slack Off
With unaware, volcarona cannot sweep past it at all, even if it does carry neutral coverage it simply cannot muscle past it, it requires tera blast water/ground for 2HKO's but it cannot physically pull a 2HKO when skeledirge counter balances quiver dance. This makes skeledirge an excellent fail-safe phaser against volc preventing it from sweeping at all, and deregulating volcarona to either a last-mon cleaner (post skele removal) or a dead teamslot since it'll just be responded to with skeledirge anytime it wants to do something.
Psychic and Hurricane (lol) are its only neutrals but again, unaware so it'll tank psychic even if it tera STABs it;
252 SpA Tera Psychic Volcarona Psychic vs. 248 HP / 252+ SpD Skeledirge: 132-156 (32.1 - 37.9%) -- 93.5% chance to 3HKO
Phasing in general is really good into volc, hazing comes at a risk cause most hazers will lose to giga drain or psychic and aren't really that useful in OU to begin with. Skeledirge is a solid tank when the meta isn't in an overabundance of soon to be rarer dark types (AND HIS NAME IS VOLCARONA!). Its just a good way to make sure volcarona doesn't get to play the game, there's no singular volc set that appreciates an unaware mon immune to burn and able to spook it out. If you want to be cringe and volcarona isn't substitute or ghost/fire resisting, you can pull a +6 off torch song - > crit fish for skeledirge to kill the volc itself (in a last pokemon is skeledirge vs. last pokemon is volc scenario).
And just for context sake, yes tera blast ban was a big hit for volc to be able to beat stuff like this;
252 SpA Tera Ground Volcarona Tera Blast (80 BP) vs. 248 HP / 252+ SpD Skeledirge: 234-276 (56.9 - 67.1%) -- guaranteed 2HKO
over the next few days. I think the combination of levitate + ghost rears its ugly head now that a few players lose access to coverage. 