Well unpredictability can only get you so far. Landorus-T can be Defensive Rocks, Defog, SD+RP, SD+Sub, Bulk Up+RP, Suicide Lead, SmackQuake, or QuakeTurn, and you can even honestly run Calm Mind sets if you wanted to.
Unpredictability isn’t inherently broken or even useful. Would not knowing Mew was running Screen before it used them really made you lose the game? And that’s assuming your opponent didn’t give it away through team preview.
With Dragapult it’s busted since Dart Dance sets have very specific counters in Unaware and Priority (where often you’ll need 2 priority users and to sack something), and then it’s Hex set completely invalidates those counters when every priority aside from Vacuum Wave is Physical (while also having a 130 BP STAB move hurled at them) and Unaware Pokemon are usually physical walls.
There is also the fact that Dragapult is capable of setting up on a lot more Pokemon than Dragon Dance Mew due to it’s absurd speed stat, defensive profile, and hitting way harder with 120 Atk effective 100 BP STAB vs 100 Atk 85 BP STAB.
But more importantly is that imprison still seems like the only problem here. Checks like Grimmsnarl and Klefki only really fail against Imprison sets, and Klefki can beat those sets too with regular Switcheroo set or Switcheroo with Imprison itself if you really wanted to make sure.
But you solve those issues with Mew anyways by restricting Imprison, as it’s unpredictability isn’t so deadly as compared to something like Dragapult.
On a different topic;
Heatran @ Binding Band/Throat Spray
Ability: Flash Fire
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Metal Sound
- Magma Storm
- Earth Power
- Taunt/Toxic
With Unaware Clefable being so common, this Heatran set take advantage of the fact that Clefable is not running Magic Guard and that Unaware doesn’t account for the user’s own stat drops. Metal Sound, while Nasty Plot would be better, acts as a psuedo Nasty Plot that is worse in every scenario except up against Unaware Clefable because Clefable’s SpD is still halves by Metal Sound. There is also basically nothing baring an opposing Heatran that wants to switch into Magma Storm while having their SpD lowered by 2 stages.
Binding Band makes Magma Storm’s residual damage even stronger, so even against something like Blissey or the Slowtwins, who do not like Metal Sound anyways, they’ll take a disgusting amount of damage.
252 SpA Heatran Magma Storm vs. -2 252 HP / 4 SpD Blissey: 253-298 (35.4 - 41.7%) -- 0.4% chance to 2HKO after trapping damage
252 SpA Heatran Magma Storm vs. -2 252 HP / 252+ SpD Slowking: 110-130 (27.9 - 32.9%) -- guaranteed 3HKO after trapping damage
252 SpA Heatran Magma Storm vs. -2 252 HP / 0 SpD Tapu Fini: 130-153 (37.7 - 44.4%) -- guaranteed 3HKO after Leftovers recovery and trapping damage
The extra trapping damage is nice since Taunt is usually the safer follow-up than to use Metal -> Storm.
Additionally, Heatran can run Throat Spray, which makes Magma Storm hit like it has 300 BP if Metal Sound succesfully hits, but this does mean that Heatran loses the power if it switches out.
Screech and Metal Sound/Acid Spray seem pretty underrated, as not every Pokemon has access to Sword Dance or Nasty Plot, and they are also useful against Bulk Up, Calm Mind, Cosmic Power, and Unaware respectfully. Another Pokemon like Crobat can run something similar as it doesn’t get Sword Dance for Brave Bird.
Edit: Gonna be honest with you all and say I don’t know how much longer I can take this meta in its current state. It’s basically unplayable currently because for some reason Dragapult wasn’t just Quick Banned like Volcarona, and other things like Tailwind not being restricted and how constrained the meta is. The deadline for the Dragapult and Kartana Suspect literally only leaves 2 days left after before it gets replaced by another meta for the month, and of course suspect tests now don’t ban the Pokemon while testing the meta (which is honestly why I avoid modern suspect tests). And that’s just a few issues with the meta as a whole. There is still Imprison, Tailwind, Clefable, and the near impossibility of revenge killing in this meta.
Maybe things will get better the 26th when (not if) Pult is banned, maybe there is a miracle where it’s banned sooner, but for now I’m not touching the meta. It’s just not fun currently.