Okay so I've been holding off on saying anything about this because I thought people were beginning to see the light but when I'm still seeing people post about it everywhere I feel like I need to finally get this out there. This is going to be a book so I apologize in advance.
Pheromosa is overrated as fuck, and is definitely not suspect worthy in the slightest at this point in the meta.
Okay so the biggest reasons why people consider Pheromosa overwhelming is because of its impact on offensive teams. Its Speed tier is insane because it outspeeds most of what is found on offense, it has great offenses to hit pretty damn hard, and it has a very strong STAB move in HJK, as well as STAB U-turn, Ice Beam for Landorus-T, and Poison Jab for Fairies. So why is Pheromosa overrated? Well for one thing, when it's not facing an offensive team, it has so many issues. Bulkier builds usually pack Pokemon such as Tapu Fini, Mega Venusaur, Amoounguss, Buzzwole, Toxapex, Mega Sableye (on stall) and Alolan Marowak, which just don't really give a fuck about Pheromosa at all, and all heavily pressure it from clicking HJK, which is its strongest STAB move. U-turn, albeit far from weak, just doesn't do enough to fat Pokemon such as Tapu Fini, Venu, or Sableye to really put it in range of so many other Pokemon. And on top of that, so many of these Pokemon are very easy to fit onto teams because of their synergy, so Pheromosa will basically be sitting in the back doing nothing until all of these Pokemon are gone, and most likely, any smart player isn't going to let that happen easily. And that's just the Pokemon that beat it defensively.
Offense has plenty of Pokemon for it too, but obviously because of its Speed stat, it's not as easy, but still perfectly manageable. Priority is very common on Pokemon such as Mega Metagross, Scizor, Ash Greninja, Mega Pinsir and both Zygardes (prior damage of course). Its Scarf set is very fast, but the biggest issue is that it just can't afford to spam HJK at all until very late into the game, because there are still plenty of Pokemon that can live a hit and OHKO in return, and that brings me to my biggest issue with it; Pheromosa has zero defensive utility. In a more offensive metagame, having good defensive synergy on an offensive team is actually very important, because it allows you to pivot into resisted attacks when needed in order to gain momentum, as well as potentially resisting sweepers that rely on priority to sweep. Pheromosa has some of the worst bulk in the tier, and because of that, anything it fails to OHKO, will most likely OHKO it in return. On top of that, by using it on your team, you're basically giving up a teamslot that could be used for something else that could potentially help you switch into a BP from Mega Sciz, Mash from Metagross, Tapu Koko's Thunderbolt, etc. It's purely put onto teams for its offensive capabilities, and while there usually isn't anything wrong with that, Pheromosa just doesn't have the ability to pressure the metagame so much to a point where every time it comes in it's usually going to get a kill. Just look at something like Hoopa-U. While it has decent special bulk, it has very little defensive synergy, and it's primarily used for its wallbreaking abilities. But the thing with Hoopa, is that every time it comes in, it's a lot more punishing, considering that the only thing that really switches into Hoopa reliably is AV Magearna. And despite Hoopa's shit defensive utility, it still finds opportunities to come in on weaker special attacks and or Psychic moves. So while Hoopa sort of forgos a teamslot for less defensive utility, it's so threatening offensively that it's well worth the sacrifice.
Pheromosa is completely dependent on momentum and free switch-ins to get it in. You are forced to make doubles, sack something, or U-turn/Volt into it. But you'd think it'd be worth the payoff considering how devastating Phero is right? Well not really. With how easy it is to punish Pheromosa's main STAB in HJK, half the time it will just come in and click U-turn, which wont be dealing a huge amount of damage to much. So if you think about it, why spend so much time trying to get Pheromosa in when you'll just end up U-turning anyway? Seems like a bit of a waste. I'd rather use that free turn for something like Hoopa or Ash Gren which are much harder to punish/switch into overall. The only sets that seem to punish switch-ins, are Specs or Quiver Dance, because a Specs Bug Buzz hits very hard and chips stuff like Fini and Buzzwole a LOT more than Scarf or LO. If Scarf is locked into any move that isn't U-turn, it's easily punishable and something on offense like Salamence, Mega Pinsir, or Landorus-T could use it as set up fodder if it's not locked into Ice Beam. Being locked into something like Ice Beam and Poison Jab makes it extremely vulnerable anyway. Its coverage moves also just don't hit hard enough, so stuff like Fini can come in even on Poison Jab. Life Orb gives it a lot more firepower, but then it has to worry about basically every Scarfer in the tier revenge killing it, as well as being very prone to being put in range of practically every priority move in the tier. And while I like Specs and QD, they still have similar issues with all of its others, in which they all lack defensive utility, require free turns to get in safely, and if they fail to kill something they die. I see it being compared to Deoxys, but the difference with Deoxys is that its coverage moves are much stronger than Pheromosas, while also having an extremely brainless STAB move to spam in the form of Psycho Boost. They're not really that comparable other than that they're purely offensive based.
But yeah, I'm just really not seeing how Pheromosa is broken at all. It doesn't force you to use obscure Pokemon to check it, because most of the Pokemon that do are some of the best picks in the meta. Outside of being annoying for offense, it has a really hard time doing much versus most builds, as they are just so well prepared for it without even really trying. Every time I've used it, I always felt like it just sat there and didn't really do anything, and the times that it had a chance to do something, I usually just ended up bringing in something more reliable anyway. While it's annoying for offense, it's far from being unmanageable. I mean, I think it speaks volume that you really just don't see it that often in a lot of higher level games. Hell, in one of the more recent SPL matches where Snow brought it vs DD, the only thing it did the whole match was just Rapid Spin hazards away, and DD's Tapu Fini forced it to click U-turn throughout the match until in the end when it failed to even kill an AV Torn-T at like 58%. It wasn't this "extremely pressuring" force that people make it out to be. The only sets that even scare me are its Special sets, and even then, Focus Blast is very risky to use because of its fragility so you're pretty limited to using Buzz, and with QD you have to depend so much on forcing switches to set up, and even then a +1 Phero is still not 6-0ing any well built team.
tl;dr Pheromosa is by no means bad, but it's not broken in the slightest.
PS: Fuck P2