Alright, I'm sorry in advance for shitty quality in this post, but it's past midnight and I doubt I'll have time to write this some other time soon, so I'll go ahead and do this now. I'll try and get through this soon.
From what I've gathered from the posts so far, they've mostly been lists of Shiftry's qualities, which I am gonna go and assume most people know, as opposed to its actual effect on the metagame, where a broken mon like it would definitely invalidate certain mons or force them onto teams, right? UC alluded to it in his last paragraph, but I've really not seen any proof of it, so I intend to actually evaluate how different playstyles deal with Shiftry.
Offense
As we all know, offense is both the best playstyle against Shiftry and my preferred style, but why is that? Why is it that offense, the best style in the meta right now, can actually deal with Shiftry? That's because it's slow. Very slow, even, for a frail offensive mon, relying basically completely on Sucker Punch to make up for that low Speed. However, Sucker Punch is easily played around and isn't exactly particularly strong either without a boost because of its 70 BP. So, now you might be saying 'but if your faster mon is chipped it'll die to it anyway'. And you're right. Luckily, any well-built offense should have 2 Pokemon faster than Shiftry
at least. Base 80 Speed is not that great, and it usually runs Adamant on top of that, so between Pinsir, Swanna, Electivire, Scarf Abomasnow, Monferno, Floatzel, offensive Silvally, Kadabra, Rapidash (seriously start using Rapidash more), etc, there's really a lot, and I mean a LOT, of great mons for offense that outspeed it that can take a +0 Sucker Punch (or, in Swanna's case, have a good chance to live one even after Rocks while giving it a run for its money with the Roost mind game), some of them even capable of taking a +2 one, like Monferno, Sash Kadabra, and any HP invested Silvally (or, you know, a Dark-resistant one). And this is before even considering the fact that Choice Scarf exists!
Also, real quick, to bring attention to this calc in UC's post:
+2 252+ Atk Life Orb Shiftry Sucker Punch vs. 0 HP / 4 Def Combusken: 203-240 (77.7 - 91.9%) -- 31.3% chance to OHKO after Stealth Rock
...this is not a good thing. This suggests Shiftry either won the mindgame of SD on Protect, even though Combusken really doesn't have a reason to Protect since it lives any +0 hit, or was already +2, which I mean fair but it got a prediction right, does it not deserve a 30% to beat a check?
Now, sure, all of these faster mons can be whittled down, many of them lack recovery, yadda yadda. And yeah, that's true. However, if a player manages to wear down their opponents team over time in order to put their Shiftry in a position so that Sucker Punch eventually kills everything, does it not deserve that reward? Again, 70 BP is weak as shit and it really needs that +2 to kill many of these mons, which isn't easy to get, and even then it's still praying that none of them have Substitute to avoid Sucker, at which point nothing mattered at all. Hell, Rapidash can just WoW it to say no to it completely.
Oh and Machoke is perfectly viable on offense too, which is just even more ass for Shiftry.
Balance
Okay, let's move on from the archetype Shiftry's worst against (which also happens to be the best in the meta right now, not a good sign for it, but okay), and discuss the one it's best against. Because yeah, admittedly, balance struggles with Shiftry. It really, really does. It can't stack faster mons effectively enough to reliably revenge kill Shiftry, nor can it have enough defensive mons to deal with it reactively. Its best hope is really to prevent it from setting up, but that can be hard at times. Or defensive Monferno, but that's quite a niche set, so fine, I'm willing to ignore it.
However, even against this archetype, Shiftry struggles to do its job completely on more than one occasion, and that's mainly due to it needing LO to really be an effective breaker more than once (this is the issue with Grassium Z btw), which results in it killing itself pretty damn quickly. Add onto that that Grass is an atrocious offensive typing, leaving it to rely on Dark for the most part, and you got a mon that, even in its best matchup, can just sort of die before accomplishing quite enough. An experienced player piloting a well-built balance will not be happy to see a Shiftry, but they also shouldn't just be giving up. Wear it down, pressure it with the faster mons you do have, and maybe force it to drop momentum sometimes.
Stall/Semistall/Other bulky teams
Full disclosure: I don't play this archetype. At all. I don't build it, I don't get how to play it well, so I really don't intend to linger on this for a long time, but basically, stall has all the tools it needs to just wait out Shiftry's PP and Life Orb with the likes of Avalugg, Altaria, Machoke, Granbull, even Togetic, and whatever niche mon
kay is gonna come up with next week. Who knows, maybe Vullaby's gonna be stall's new face, I don't get that guy. Again, wearing it down and preventing it from coming in as much as you can shouldn't be too bad.
General flaws
So, now that we've gotten its spot in the meta out of the way, let's talk about how Shiftry isn't the perfect god being the previous few posts have described it as. First off, and most importantly, Shiftry is
not easy to get in. Every post so far has glossed over this fact that in order to actually get something in, a player has to either make a proactive play like doubling or using a momentum move (admittedly not that taxing, but with several of the mons Shiftry preys on, like Golem, being immune to Volt Switch, it at least makes it slightly harder), which deserves to be rewarded, or their opponent has to not realize 'oh hey, if I grab this kill on Swanna with Bronzor, Shiftry can come in and threaten me. It's more effective long term to switch out right now into something like Watervally', meaning they make a mistake, which should be punished. In addition, it's complete ass against faster mons with Sub, which should be more common than they are because damn is Sub a good move. And, lastly, if it makes a wrong prediction by, for example, setting up an SD on a switch to FightingVally, then it immediately puts its team on the backfoot. All in all, Shiftry is too hard to get in and too prediction reliant when it is in to be broken, in my opinion. The previous posts have looked at it mostly in a vacuum, where it's certainly good, but that's not entirely fair.
Yes, Shiftry's a great breaker. An excellent one. But this call for a test is, in my opinion, just another response to a good mon showing that it's good, like happened with Floatzel, Pyukumuku, Komala, Pinsir, Electivire, and even currently, Swanna. All of those received calls for tests until we realized 'oh never mind they're fine if we just change our builds slightly'. Monferno, Rapidash, and Granbull aren't unviable by any means, Sub on faster mons isn't that bad. Build with it in mind, and you'll be fine. At least, that's been my experience.
EDIT: apparently the main point of my post wasn’t clear. I currently don’t believe Shiftry’s broken, yes, but I mainly want to encourage people to put things in context instead of just looking at Shiftry in a vacuum.