First and last post I will be making here because I don't want to stress myself out by reading this thread more than I already have.
Quite frankly, if anyone is phrasing the Pex/Ferro argument as them WANTING to run SpDef, they should stop doing that immediately. That is not remotely the case. It's not necessarily true that they WANT to be SpDef, it's that they have the FREEDOM to be SpDef.
I'm going to divide the next part of this post into two sections: one about what the meta would be like
without Vish, and one about what it would be like (and currently is like)
with Vish.
Without Vish: If (when) Vish leaves, Ferro and Pex will have significantly more freedom in their EV spreads than they currently do. As has been pointed out by previous posts, Ferro and Pex both traditionally ran SpDef sets in the last generation, both of which could have their merits in the current generation. With full SpDef investment, both of these mons become to Dragapult what SpDef Clef is to it currently: a bulky target that even Modest Spell Tag Pult will struggle to break, provided each still has its Lefties or Black Sludge. Here are some calcs comparing the rolls for PhysDef vs SpDef variants of the mons in question (assuming it's Thunder Wave Pult for both, so burn damage doesn't play into it).
Pex
252+ SpA Spell Tag Dragapult Hex (130 BP) vs. 252 HP / 4 SpD Toxapex: 171-202 (56.2 - 66.4%) -- guaranteed 2HKO after Black Sludge recovery
252+ SpA Spell Tag Dragapult Hex (130 BP) vs. 252 HP / 252+ SpD Toxapex: 132-156 (43.4 - 51.3%) -- guaranteed 3HKO after Black Sludge recovery
Ferro
252+ SpA Spell Tag Dragapult Hex (130 BP) vs. 252 HP / 4 SpD Ferrothorn: 204-241 (57.9 - 68.4%) -- guaranteed 2HKO after Leftovers recovery
252+ SpA Spell Tag Dragapult Hex (130 BP) vs. 252 HP / 252+ SpD Ferrothorn: 153-180 (43.4 - 51.1%) -- guaranteed 3HKO after Leftovers recovery
Specs Aegi is also less of a factor if Pex is allowed to run SpDef, as Specs Shadow Ball cannot 3HKO and it's able to Recover the damage off. The same goes for Ferro (I'm too lazy to post calcs for this one so you can verify it for yourself if you want). And though this is probably not the most consistent answer, SpDef Pex is guaranteed to live one +2 Rotom-H Discharge from full (barring a crit ofc) and can use that as an attempt to either chip with Scald or cripple it with some kind of utility move (i.e. Toxic or Knock Off if it has them). In the current meta that last sentence might seem
completely irrelevant given how common Baneful Bunker is over Toxic or Knock at the moment, but I hope everyone remembers WHY Bunker is so common (hint: it's the subject of this entire thread).
Now, do Ferro and Pex HAVE to run full SpDef in this hypothetical Vishless meta? Absolutely not. In fact, there are still situations where PhysDef could be useful on these mons. For example: aside from Clef balance, one of the most common playstyles at the moment is sand, and of course the star of that show is Excadrill. Pex is obviously not much of a consideration when dealing with Drill, but Ferro, as we all know, learns Body Press. And if Ferro goes full SpDef, Drill only takes around 60-70% from Body Press. Still a 2HKO, clearly, but it pales in comparison to the 80-94% Drill takes from a full PhysDef Ferro. The important thing here, though, is that they can
CHOOSE. The things that each spread would help beat have other switchins. They don't HAVE to run one spread; they can go PhysDef OR SpDef. Hell, maybe they can even run mixed defense spreads. No one really does that anymore so I don't have a set on hand, but there's probably some way to make that work without Vish here.
Now going on to the next segment...
With Vish: I don't think I have to really say much at this point. We all see how the meta currently is with Vish; there are approximately 3 worthwhile mons that can even avoid getting 2HKOd by Fishious Rend, and approximately 0 of them can 2HKO Vish in return. All three of those mons run full PhysDef investment almost exclusively because of Vish, and even then Ferro is the only one that can't be 2HKOd by one of Vish's non-Rend moves (not that that matters much, since even with Lefties it can almost be 2HKOd by Banded Rend and has no recovery to mitigate that). I could echo the points of so many people, but I think I'll choose to only echo
McCoolDude, who has without question my favorite post in this entire thread.
If a mon with BASE 131 DEFENSE (aka Ferro) is literally
required to be PhysDef in order to avoid being 2HKOd by a specific,
resisted physical attack from full -- and if that specific physical attack is only learned by one (usable) mon -- is that not a sign of a mon being unhealthy? I think it is.
TL;DR: Without Vish present, Ferro and Pex have the freedom to choose different EV spreads, rather than being forced to run max PhysDef to only just barely protect themselves against one specific, incredibly team-restricting mon.
And since this response has mostly been responding to the Ferro/Pex part of the OP, I'll take a little time here to talk about the Seismitoad part too.
Tacotaco is right in one regard -- mediocre mons CAN become good for the current meta because of other popular mons. That's how we ended up having Flareon on the SSOU Viability Rankings for like a month(?) earlier into the meta. Back when Clef's most common set was 3 attacks + Life Orb, Flareon was ranked (albeit only around the C tier range so maybe not so good after all) due to its ability to devour every move LO Clef ran as well as its ability to Wish pass. It was also somewhat bolstered by its ability to check the Specs Pult that were so common at that time, despite doing jack shit in return. Then, once the dust cleared from our eyes and we remembered that Rotom-H exists, Flareon dropped off the face of the Earth and hasn't been heard from since. The difference between Flareon and Seismitoad's situations, however, is that there were other options where Flareon was concerned. In contrast, looking at Toad through the lens of the Vish meta, there is literally nothing else that offers what it does right now. It's one of very few usable Rend immunities, and it's the ONLY one capable of running Rocks, Knock Off, AND Toxic. Look at it without the Vish context, though, and the reasons to use it over Hippowdon are basically nonexistent. Hippo is bulkier, can also set up Rocks, can remove setup sweepers with Whirlwind, AND has reliable recovery.
Trust me, I have no ill will towards Toad whatsoever. As a matter of fact, for my own personal reasons, Seismitoad is actually my second favorite mon. Period. But when you look at the physical attackers in OU bar Vish -- Drill, Bisharp, Terrakion, Conkeldurr, hell even Crawdaunt with Knock Off -- and compare how much Toad takes from them to how much Hippo takes, it's not really much of a contest.
I apologize for making this post so long, but as I said at the start I don't really wanna contribute much to this thread. I just wanted to make one post and be done with it, since reading some of the comments here has already raised my blood pressure a bit too high. Goodbye and goodnight, my friends; it is now time for me to mute this thread.
