You know what, I inspired myself. If you guys wanna see me do another thing being talked a lot about, just ask. And mind, writing this takes a while, so gimmie a moment if I do it.
So anyway, let's objectively analyze Comaphaze, shall we?
Compahaze itself
This particular strategy is not any one given move or ability. Comaphaze requires Comatose, Sleep Talk, and a shuffling move, such as Dragon Tail or Whirlwind, on a fast Pokemon to function. Some sets require entry hazards in order to do damage, but not all do. Most Comaphaze teams cannot reliably KO the last Pokemon with. A properly executed Comaphaze strategy prevents the opponent from having a turn to act until they are finished, outside of manually switching their Pokemon.
Comatose treats the ability user as if they are always asleep, rendering them immune to all non-volatile status, preventing use of Rest, and allowing the use of Sleep Talk. Comatose is limited by Ability Clause, restricting the strategy to no more than two Pokemon per team under normal conditions. In theory, it is possible to have six Comaphazers, but this requires cooperation on part of the opponent and should not be a serious consideration.
Sleep Talk calls upon a random move in the movepool other than itself, with the exception of Assist, Bide, Bounce, Chatter, Copycat, Dig, Dive, Fly, Focus Punch, Me First, Metronome, Mirror Move, Razor Wind, Shadow Force, Sketch, Skull Bash, Sky Attack, Solar Beam, and Uproar. Sleep Talk is stopped by Taunt. It also only has 16 PP.
Shuffling moves are Whirlwind, Roar, Dragon Tail, and Circle Throw. The first two function similarly, being bounced by Magic Bounce, but otherwise bypassing Substitute and Evasion. Roar is also stopped by Soundproof. Circle Throw and Dragon Tail bypass Magic Bounce, but are stopped by Substitute and type immunities. By using Sleep Talk, the negative priority of these moves is completely bypassed, allowing them to be used at +0 priority.
Compahaze Abuses
Compahaze is almost a play style unto itself. However, the strategy falls under stall by definition, though some offensive and balanced teams can easily benefit from having one or two users as well. Stall might use the strategy to as the main source of their damage, whittling down the opponent before inflicting a different source of residual damage defeat the survivors. Offensive teams can use the strategy to soften up the opposing team before setting up for a sweep or using something fast and hard hitting to directly clean-up.
Priority is a possible concern for Comaphaze strategies as it lacks its own priority. Psychic Terrain, whether by the move itself or Psychic Surge can temporarily provide relief to a Comaphaze team from being shut down with priority. Dark-types also work as well for dealing with Prankster, such as Ash-Greninja.
Fast Pokemon, such as Deoxys-Speed, Ash-Greninja, Mewtwo-Mega-X, or Pheremosa, are often running the strategy, using their high speed stat to outpace the competition and act before the opponent does. These Pokemon can opt to run a Choice Scarf to ensure that they cannot be outsped except by priority and other scarf users.
As Comaphaze only has 16 PP, a team is limited to only 32 uses. Leppa Berry can potentially extend this by another twenty.
Hazards, such as Stealth Rock, Spikes, Toxic Spikes, and Sticky Web, are almost always deployed in conjunction with the strategy to whittle the team down farther. Stealth Rock is quick to set-up and is still the premiere hazard and can be enough against most teams to rack up the necessary damage to secure a win. Spikes and Toxic Spikes are less frequently used, but can whittle down a team even quicker. Sticky Web helps ensure the opponent will not be able to outspeed, even with a Choice Scarf, and can also allow for slower, less expected Comaphazers to do their job.
Circle Throw and Dragon Tail allow a Comaphaze team to freely inflict damage if hazards are not set-up. Depending on the users, this can be chip damage, such as from Deoxys-S, or quite painful, such as from Choice Band Mewtwo-X.
Of the moves Sleep Talk does not call, Comaphazers can run Assist to access potentially powerful moves without running the move themselves, depending on how the team is built. This requires a dedicated team, of course. But, as Assist will not call Sleep Talk nor shuffling moves, a Comphazer can be placed onto an Assist team with little risk to the strategy.
Perish Song can be used to cleanly deal with the last surviving Pokemon. If the Comaphazer has four Pokemon left when using the move, they automatically win if the last survivor is not Soundproof.
Comaphazers are able to use other moves that Sleep Talk does not call to fill in extra moveslots. While most of these moves are not great, it gives the Comaphazer extra function once their Sleep Talk PP runs out. Chatter is the notable exception, being the only move on the list banned as of this writing.
Comaphaze Counters
The most complete counter is Magic Bounce Mimikyu, who is immune to all forms of shuffling. However, Mikimkyu offers very little use in Balanced Hackmons outside of this role and can be potentially bypassed with a move such as Shadow Force.
The next best thing is probably Suction Cups, as it stops the shuffling completely. However, the ability has little merit in BH beyond stopping Comaphaze or for anti-Imposter strategies and, in any case, it still takes damage from Dragon Throw.
Comaphaze Checks
Another good answer is Prankster. As Sleep Talk is a non-attacking move, it is stopped by Taunt. However, due to the speed of the strategy's abusers, it is often required to use Prankster. Likewise, Torment severely hampers a Comaphaze strategy and can do so until the user switches out. However, it suffers the same problems as Taunt and, additionally, has lesser merit to be ran outside of very niche strategies. Residual damage, such as Toxic, Will-o-Wisp, and Leech Seed can help wear down a Comaphazer faster. All of these, however, are stopped by Psychic Terrain and Dark-types. Substitute can be used to help stop direct-damage versions, though is useless against Roarwind.
Magic Guard bypasses damage from hazards, the often the biggest source of damage from the strategy, though can still be whittled down by the direct damage shuffling moves.
The use of Magic Bounce and Magic Coat can stop non-damaging Comaphaze variants, but does nothing to Dragon Throw.
Protect moves, particularly Spiky Shield, King's Shield, and Baleful Bunker, can stop and punish Dragon Throw, but does nothing to Roarwind. Dragon Throw also suffers from Rocky Helmet, Rough Skin, and Iron Barbs, though these are niche items and abilities otherwise. Flame Body, Cursed Body, Effect Spore, and similar abilities can also have a chance of interfering with the strategy, but otherwise have little merit.
Soundproof stops Roar and also has the added benefit of handling Boomburst Refigerate, Pixelate, Aerilate, and Galvanize. It does little else, however.
Priority, particularly Fake Out + Extreme Speed, often with -ate or Galvanize, can offensively defeat most Compahazers. However, Psychic Terrain stops them in their tracks and bulky Comaphazers can survive to continue whittling them down.
Up to two Pokemon can weather the storm with Regenerator. However, only certain Pokemon with the right typing can do so against all forms of hazards, such as Solgaleo. Anything weak to Stealth Rock or vulnerable to grounded Poison status risk getting whittled down slowly through Regenerator. Additionally, Dragon Throw can add damage to overcome the Regenerator, even just barely. Some extremely niche Pokemon at best, such as Skarmory and Landorus-Therian, have the typing ignore most hazards without being weak to Stealth Rock. These Pokemon are largely useless to most teams, however.
Pokemon with Poison Heal are immune to Toxic Spikes and can shrug off damage from one layer of Spikes or neutral or resisted Stealth Rock, allowing them to weather light hazards with Roarwind. More hazards or Dragon Throw will overcome their healing.
Typed-based immunities from Ghost and Fairies can defeat Dragon Tail or Circle Throw, but not both, and still lose to Roarwind without abilities.
Contrary can get a speed-boost from Sticky Web teams, allowing it to potentially outspeed the Comaphazer.
Rapid Spin and Defog remove hazards, but do not mitigate Dragon Throw damage. Additionally, they can be hard to pull off outside of Prankster Defog once the strategy is going.
Imposter can win a speed tie against some Comaphazers, but loses to Choice Scarf.
Ingrain stops all phazing, but is hugely risky as it stops all switching outside of moves like Volt Switch. This can potentially allow the opponent to set-up for free on the Ingrain user or simply KO them with Perish Song.
So what makes Comaphaze suspect worthy?
The strategy has no reliable counters outside of Pokemon and abilities that really have little to no business in Balanced Hackmons to begin with. There is a plethora of checks to the ability, but failing to bring multiple, correct checks can potentially mean a match against a Comaphazer is decided at team preview. Two magic bouncers are helpless against two Dragon Throwers. Choice Scarf Taunt Deo-S loses to Sticky Web. And so forth. A team much bring at least two Pokemon with solid answers to Comaphaze to cover most common variations. And even then, checking it may devolve into waiting for the right Pokemon to be phazed in, which is purely RNG.
Most importantly, however, once the strategy is going, and the opponent lacks the correct checks, the battle becomes non-interactive for at least 16 turns and up to 52 turns. An opponent on the receiving end literally cannot do anything other than manually switch, which is potentially a bad idea as that just racks up more hazard damage. As such, they are simply forced to wait, removing any element of competition from the battle until the strategy has ended.
The sheer number of checks means the strategy, however, isn't inherently broken. It cannot win a battle on its own either, a third Pokemon, or at least other moves, are usually required to finish off the last survivor. Which means, while unlikely, a comeback is possible if the victim endures the comaphazing.
So my stance?
This is purely opinion. I've stated it before, but am doing so for the sake of this post. While not necessarily "broken" or "overpowered", I still firmly believe comaphaze is unhealthy and potentially over-centralizing. If you're not prepared for it, you either lose or at least suffer greatly. The whole point of the strategy is to prevent interaction between the opposing teams while the phazer does its magic, making the match one-sided and, IMO, unfun. This is bad for metagame health as it discourages players from actually playing. While there's no official guideline for this, I feel causing players undue frustration for the sake of keeping something that's "not broken" to be a poor decision for the future of the meta. We play for fun, after all. And if a meta isn't fun, it's simply not played.
Comaphaze has two lynchpins: Comatose and Sleep Talk. Banning one crumbles the entire strategy. As such, I feel Sleep Talk should be banned. Comatose has potential merit for other sets and strategies, such as coming up with status-immune set-up sweepers or a cleric who need not worry about sleep before getting a Heal Bell off. These things sound viable and, in the little practice I've given them, feel like it to. Sleep Talk... it only has two uses: unreliable check against sleep users and Resttalk, which, while a neat strategy, is considerably more unreliable and expensive than simply using Recover. Or even using Rest + Natural Cure. As such, Comatose should remain, but Sleep Talk should go as its removal would have the least impact on the rest of the meta.
If I missed anything, lemme know. I think I missed a check or two, but I'm fairly confident they're all fairly unreliable. On the other hand, I'm also confident there are no other counters (which, for the purposes of this analysis, needs to be able to reliably beat all forms of Comaphaze).