I believe the needle needs to be moved in some significant way, given the state of the tier.
While many people believe it to be pretty fun and balanced by broken v. broken to a point where nothing should happen, I believe that such a concept is far more tantalizing on paper than in practice. The tier is not in a sustainable state, and it's evident by how reactive it is, and the consequences of that reactivity. The metagame is incessantly changing; teams have to find new ways to respond to adapting threats, and in doing so, compromising themselves against other things. Normally this is a good thing, but in my eyes, metagames that grow this fast and have so many centralizing trends to respond to will often enter a state of oversaturation, leading to teams having to make concessions, and a more matchup oriented teambuilding experience that can be unreasonably difficult (if not impossible) to prepare for any stable threatlist with. This is the inherent problem with broken checking broken; at some point, you enter a vortex of reactive adaptations that force very exploitable weak points, and can situationally cause games to boil down to one or two key turns because of the degree of raw threat factor there is to prepare for and play against. There's a reason Stall has become so popular, because it's really the only way to contain as much as possible while keeping your options open. But even then, it isn't enough sometimes. Sure, the tier can be fun when you get the right matchups, but more often than not you will lose to polarizing threats you literally did not have the ability to prepare for without compromising yourself in other respects, or enter matchups that feel (and often can be) stacked against you.
Removing Archaludon would be a great step forward, but that doesn't remove Sun from the equation, nor does it address the copious amount of other threats in the tier that can't reasonably be prepped for in a vacuum. Pokemon like Galarian Slowking, Ting-Lu, and Great Tusk are obscenely good blanket checks to many things, but at the end of the day their utility is not all-encompassing. Galarian Slowking is extremely resilient, which makes it a potent check to Walking Wake and Kyurem. However, being weak to Knock Off (thus making it a free click) is a horrendous Achilles' Heel given the vitality of HDB to stabilize teams into hazard stack structures, and Steel-/Ground-types are very problematic for it and often not easy for it to respond to. Great Tusk and Ting-Lu are very potent defensively, but their lack of recovery does leave them prone to being overwhelmed through the barrage that is Gouging Fire, Roaring Moon, Kingambit, and more, while also being exploitable by Pokemon like Volcarona depending on your moveset. Going with these Pokemon is almost always a good choice, but being railroaded into using them to contain Pokemon that they only loosely check while preserving team synergy can often take even more control out of your hands and lead to devastating gamestates that are often unavoidable.
Regarding Tera:
Many people have attributed this level of polarity to Tera, since it's a consistent factor behind the potency of offensive behemoths, but I really don't think Tera is the issue here. If anything I've found that Tera actually grants some semblance of stability by giving teams costless failsafes into specific weakpoints, and there is a heavy element of skill involved with knowing when to use your Tera and how to play around your opponent's. Though quite obviously defensive Tera isn't enough- Tera is just as lucrative for offensive threats, and while defensive type shifting is a big element behind that, I also believe that Tera Blast is a very undersold element of offensive Tera that can outright remove checks or make them incapable of functioning through the element of surprise and coverage inflation respectively.
I am still very much so a fan of removing Tera Blast; even if it doesn't seem like it changes very much in a vacuum, I do believe it does contribute to a stupid amount of variance that compositions have at their disposal and generates more polarity by inflating movepools to an asinine extent. Kingambit, Dragonite, Volcarona, Raging Bolt, Kyurem, Dragapult, Serperior; the list goes on, because giving offensive Pokemon the ability to beat checks with unreasonable consistency and little leverage to play around only makes the current state of the metagame more difficult to navigate by adding even more matchup-oriented elements. This is honestly a huge reason why Tera Blast is worth removing to me even if it doesn't seem all too great of a target on paper. Reducing the threat level by keeping some Pokemon's matchup pool consistent can help us navigate more polarizing Pokemon like Volcarona more consistently, at least a little bit.
Regarding "Broken" Pokemon:
From my experience, the most egregious Pokemon to navigate have been Kyurem, Archaludon, Volcarona, and Raging Bolt in that order. Honorable mentions to Roaring Moon and Kingambit.
I am pretty disappointed to see Kyurem stay since I don't really think it offers anything that we don't already have, and it feels the most unreasonable to check while also being the easiest to enable. More reasoning
here. Archaludon is being suspect tested, and I've already explained my stance the best I can
here. Hopefully it leaves!
I just... don't think it is a healthy presence, so long as Tera Blast is around. I think it is the most egregious example of the potential Tera Blast has to utterly ravage Pokemon that it shouldn't, and it benefits from every aspect of the mechanic in nearly every way. It has some neat qualities defensively, but what it offers to the tier doesn't outweigh what pressure it lays on battle dynamics. I feel as though it is a really hard Pokemon to truly stop and consistently play around, even if you maneuver around it well and have some prep in the teambuilder. The variance of Tera, its moveslots, and the constant variable of Flame Body make it very difficult for teams to navigate around in the mid-to-late game when its cards are not fully out. Volcarona would be an easy save with Tera Blast in the bin, but as long as the move is around, Volcarona has a lot of variance involved with it, usually in favor of the user. I'm not super sure if I would call it conventionally broken per se, but I do think it is uncompetitive in its current state.
Raging Bolt is a pretty silly Pokemon. While it's a less egregious variant of Archaludon as a Dragon-type wallbreaker with shiny Electric-type moves, with some priority to boot for offense, it's also a nightmare to check without dedicated Special walls that also have the ability to pressure it in return or outlast it, essentially being just Clodsire, Ting-Lu, and Blissey. Most other Pokemon collapse to its dual STAB combination. In essence, it is a very anti-offense Pokemon, but is harder to get value out of against more reinforced teams that often feature Pokemon like Ting-Lu, Gliscor, and Clodsire anyway. Granted, I do think its priority is more reasonable to check than Kingambit's, seeing as Ground-types are reliable revenge killing options (barring Tera). The bulk and access to Calm Mind make it a trade artist (that can sometimes just clean thanks to Thunderclap) that is difficult to break past without making some sacrifices or maneuvering around it correctly with Pokemon like Iron Treads or Galarian Slowking and positioning a Ground-type. It's possible that reduced polarity may make it more reasonable to answer as the metagame begins transitioning into a more stable state, especially given the nature of its priority move, but I struggle to see how the needle would move to favor its presence in the long run without some level of uncomfortable teambuilder oppression, especially once Clodsire stops feeling as necessary.
I can elaborate more on my thoughts regarding the laundry list of centralizing threats later, but for the sake of not making this post a massive snooze-fest, I agree with njnp that action needs to be taken with bans in order to begin moving toward stability.
Regarding Booster Energy
I read earlier the idea of addressing Booster Energy, which is an interesting proposition that I'm extremely curious about. There is tiering precedent of banning overwhelming elements that aren't as good on other things, which... yeah? Baton Pass on a Jigglypuff isn't going to break the world, but was used broadly enough to be considered fundamentally problematic. Booster Energy isn't quite comparable to Baton Pass, but its effect is extremely felt in the tier.
it's the immediacy of Booster Energy that is really striking. Having a 1.5x Speed boost on entry with no drawback is often game-defining, and makes it easier for more offensive structures featuring Pokemon like Roaring Moon, Iron Valiant, or Iron Boulder to force you out and find opportunities to exert pressure. Booster Energy is a massive reason the tier is as fast as it is, and why priority, your own Booster Energy users, and fast Choice Scarf users have essentially become mandatory for most structures. Offense boosts can be very strong too; Roaring Moon and Raging Bolt gain very notable powerups, with the former having the perfect move to take advantage of it, and Raging Bolt having powerful priority. Offensive Booster Energy is a nice tool for Gouging Fire too, making it so it doesn't have to Dragon Dance as much to enter into a stable cleaning position. I would argue it is not quite as influential as the Speed boost, but its best users make deadly use of it.
On paper, removing it seems actually quite relieving, seeing as many users (like Iron Moth, Iron Valiant, and Sandy Shocks) live and die on the ability to outpace most of the metagame. However in practice I struggle to really extrapolate how the metagame would really reply to it, to a point where I'm skeptical of how worth it it actually is over just banning the stupid stuff, which is more feasible to extrapolate comparatively.
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Hopefully this provides some food for thought. Bear in mind that these aren't binding opinions and may change pretty quickly as we continue to discuss our approach!