Volcarona and Urshifu's ban was highly controversial. You want to know how much? Several of the OU council members received death threats for it. Yes, that's how insane the playerbase was driven for it. While the brainlet degenerates that did resort to harrassment should probably have their PCs explode in their face or FoaD, the reason for this is there was a recent survey but neither of these two mons were in it yet they were still quickbanned. It was like the OU council just gave the playerbase the middle finger and banned whatever tf they want to make the meta more balanced for I believe it was WCoP. This debate even lasted for at least 10 pages
As for the reasons why, for Volcarona specifically, it was mostly due to tera. The ability to change type at will to beat its checks is nothing to scoff at. That's a problem that the tier faces right now with the existence of the living incarnation of cancer stage 100, Kingambit. Oh, and there's also boots because boots is broken and gamefreak sucks so much balls when it comes to balancing their own goddamn game. I'll just quote the main explanation as well as the thoughts of several council members on the matter but you can read it in detail here
Volcarona has been near the center of tiering discussions for quite a few months now, predating Pokemon HOME. Unfortunately, the uncertainty surrounding HOME's release date left us unable to suspect things like it, Garganacl, or Kingambit, who drew the ire of many players. To make matters even more concerning, Volcarona came out after the release of Pokemon HOME and arguably got even stronger as it employed a wider, more practical array of Tera types and was able to focus on offensive variants as the developing metagame trended in that direction. Many people argue that terror of Volcarona is more of a mechanical issue with the core of the metagame, but that is a discussion that cannot be tackled just by a single council vote and will be brought up to the community for a greater discussion in the coming weeks. In the meantime, we are left to focus on Volcarona in the current metagame.
Offensively, it can handpick its own counters. Scared of Heatran walking normal moves? Tera Water and Tera Ground do the trick. Skeledirge falls into the same boat, of course. Scared of revenge killers with priority? You can run Substitute for Sucker Punch or Tera Ghost for ESpeed as I mentioned before while hardly any scarfers do the trick after a Quiver Dance. Even things like Clodsire can lose to Substitute + Tera Grass, but at least this and bulkier variants have fallen out of favor with Heatran’s release. Given this, there is at least some counterplay and some intuition that can allow for eliminating some options or forming a hypothesis as to what Tera and set it may be. But is: that enough? I don’t really think so.
I intend to be voting ban on Volcarona . I've found the Pokemon to be rather uncompetitive for months and home hasn't really changed that...in fact it has made things worse with how Volcarona has adapted its tera and certain checks no longer are able to handle it. I've been discussing this for weeks internally and amongst peers, I pushed heavily for Volcarona to be on the previous radar and now I will be pulling the trigger on voting to ban it. I find this is the most match-up skewed Pokemon and has been from the start of the tier, sure Tera makes it broken but heading into WCOP as we all know we aren't touching Tera until it has concluded. With the new additions Volc has not gotten worse at all, it's performing just as well maybe even better than it did pre-home.
Volcarona, to me, is a Pokemon whose versatility is mostly dictated by the current state of Tera in SV OU. Most of Volcarona's strength centers quite heavily around Volcarona's versatile applications of Tera, Tera Blast being able to augment its coverage seamlessly, and Volcarona being able to take advantage of nothing turns better than other Pokemon, which type shifting can create more of. I do believe that their degree of strength and Volcarona's set options are primarily enabled by unpredictability, and while this is because of Tera, I believe that Volcarona is moreso optimized at exploiting it compared to other Pokemon in the tier to where it stands out as a special case to me.
There was also one other post from OU council member named xavgb but I didn't quote him because his post is so long and not a single paragraph summarizes their issue with Volcarona. Instead, just read his post from the link I gave
