Hey look it's me I'm back again back with my fresh hot takes, and now I'm here to talk about something that's been really bothering me with the tier.
Anyway, so, I've been grinding the tier a lot, and I can't help but feel there is a huge, fundamental problem with defensive cores. Despite the tools that we have at our disposal, the tier has been fatter than it's ever been, with Pokemon like Skarmory and the buffed Teleport now running amok. Dancing around these Pokemon is a really hard task because not only are defensive cores better than they've ever been in UU, but, more prominently, positioning is easier than it's ever been, and getting into an optimal position against your opponent is incredibly easy with so many options and Teleport. You might argue there's no real use in just pivoting around to no avail, but Hazards and passive statuses are a thing, after all.

To put it in a vacuum, I think Teleport is a problem. This seems like an absurd notion to make, but I think it makes sense as to why so many Pokemon and defensive archetypes have been so obscenely difficult to handle.
Positioning against offense is really easy with Teleport, because Blissey and Slowking are not only great facilitators of the move, but Skarmory is a fantastic partner that is a great check to a lot of the tier's physical threats that otherwise bother the two. HDB also provides these Pokemon with absolutely no recoil as they freely pivot around and bit by bit wear down the opposition, all while they can stay healthy and make breaking through cores neigh impossible, since with Teleport, whether the opposition stays in or not, the Teleport user always has the momentum advantage. On top of the fact Slowking has Regenerator and Skarmbliss both are able to keep themselves healthy by merit of reliable recovery, breaking defense has been harder than ever, and I feel is a huge reason why things like Terrakion and Lycanroc, while good, are readily checkable and prone to being worn down. These Teleport users also have great partners in the form of Palossand, Weezing-Galar, and Mantine, and it's immensely difficult to break much of anything unless you get a hard read or you manage to set-up without any kind of consequence. I've found it almost needed to run a Skarmbliss check on my team just so I don't get walled out from Teleport completely invalidating reads, and even then, the other great partners that defensive cores can run can trouble those checks as well, such as Palossand for the niche Luxray (which is kind of heat tbh).
Likewise, Teleport users are incredible glues to offense, too. Getting in immensely strong breakers 100% for free is arguably part of what makes things like Durant or Scolipede so difficult to handle alongside their natural strength, and our perpetrators can be easily swapped in for their great defensive utility, and repeat the process all over again. I've also ultimately found that Slowking is the superior screen setter to Grimmsnarl in the tier, simply because as soon as you get your screens up, you can just freely pivot into your breaker, and make the offensive cycle even simpler.
The problem could also be HDB as well, which make these pivoting mons so difficult to wear down to begin with, especially with Slowking's access to Regenerator. I've seen a lot of Pokemon run HDB simply for pivoting purposes. Though, the thing with HDB is that they weren't at all broken before such great pivot mons got into the tier, and they aren't really broken on anything that doesn't blip out of the end of the turn. Additionally, they can be knocked off, but unlike on Incineroar, for example--where it's greatly troubled by hazards--Slowking and Blissey are only really inconvenienced by them. Slowking and Blissey themselves are far from being problematic on their own, but in my opinion, having Teleport makes them incredibly easy glues that can make defensive cores neigh impossible to break. This is because you'll rarely be rewarded for a read if they click Teleport, or paired offensive cores will be turned from tactful into one or two Teleports; it's blatantly uncompetitive due to how much it dumbs down the game and how low risk high reward the move actually is. Overall, Teleport is just ridiculous, and alongside HDB to lower punishment of switches, Teleport turns the game into a series of surface level plays and dumbed down game plans on offense and defense alike (but mostly defense).
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Anyway so the BL mons
Durant
I don't know if it's been because of how I'm using it, but I haven't really had the most amount of success with Durant. Though, I can certainly say this thing is an absolute powerhouse in the tier, which, along with its great speed tier, coverage, and set efficiency, is most likely warranting a ban. I don't feel as strongly about this as other people, mainly due to its frailty, chance to miss, and its troublesome case with 4MSS, but that isn't really what makes it so strong. What makes it strong is its immediate power and ability to dismantle teams with its great coverage. With your choice of LO AoA, Band, or Hone Claws, it is capable of being an immensely strong wallbreaker that makes cleaning games a lot easier, whether you sweep with Durant or not. Hone Claws is something I've particularly liked on HO and is immensely hard to check with only 1 boost--which is easy to get with its solid defensive typing, and solid bulk with the utility of Screens. Although, AoA variants are much stronger on balance for breaking necessary holes, which it will almost assuredly do. The problems with it are not only how good it is at wallbreaking, but also how good it can be at cleaning as well. Plus, as a sour cherry on the top, I don't like how RNG is a huge means of which to check it. I'm not as passionate about it as others, but I think sending it back to UUBL is fine.
Mamoswine
It pairs pretty nicely with Durant, I feel, but I can't really say Mamoswine is problematic anymore. The defensive level and speed tiers have increased tremendously, and while Mamo is going to be a tier staple again, it's certainly manageable since it is prone to being worn down and troubles to break through a lot of cores running around due to the advent of Slowking and Skarmory on top of its natural checks as is, with Rotom-W in the tier too. Unbanning it is definitely fine.
The other guys




Of these, the only one I could see being feasibly tested is Diggersby or maybe Venusaur, but even then those might be a bit of a stretch. Something I noticed with these Pokemon is that they all spearheaded an aspect of certain archetypes or outright invalidated other archetypes. Venusaur made Sun obscene, Ninetales made HO obscene, Haxorus shut down Balance and Stall indiscriminately, Dracozolt shut down Stall and Balance indiscriminately, and Diggersby shut down Balance and Stall indiscriminately. I think these guys deserve to be kept behind bars, mostly because they are far, far too much to handle in game, and require too much dedicated prep to actually be handled, which obviously isn't healthy. It's probably best to leave these guys alone.