Solo Azumarill rolled all over the Salamence raid, literally. It did get kind of annoying to manage setting up against, with both Moxie and hybrid Tera Blast and also being immune to the typical Mud-Slap, so trying to out-defense on either side it is a problem even with great AI. But it turns out Azumarill can certainly out-offense it, being weak to Rollout makes the optimal strategy pretty simple with the press of a button. Even with its shield up from around full HP, 3 fully boosted Tera Rock Defense Curl Huge Power +6 Rollouts can break through the shield cleanly, and a 4th will kill on the free turn afterwards if it lands.
Raid script from
https://stevecooktu.github.io/sv_raid_lookup/. Overall a 450s/7.5 minute raid like Tyranitar, with the same 40% HP shield and the usual 40% HP trigger for double attacks with this set of raids (telegraphed with Dragon Dance). The shield goes up really early too.
EDIT: Fortunately, Salamence has quite a few vulnerable periods to allow keeping up buffs and debuffs for most of the relevant part of the raid.
I locked in a pretty solid AI group of Tauros/Gardevoir/Staraptor, 2 Intimidates and a Life Dewer keeps Salamence's Moxie snowballing constrained to just net gains off killing Gardevoir (and me), though it does leave it with Special Tera Blast for a while, and you do have to wait and make sure the AI respawns and activates Intimidate before inputting an attack. I think the AI actually have increasing respawn cooldowns as well after noticing I had to wait on them for a while. Gardevoir can also potentially Synchronize Burn off of Heat Wave/Flamethrower.
I was experimenting with Muddy Water accuracy drop strats (though Muddy Water is a DLC-exclusive TM option which I didn't want to resort to), with a Zoom Lens for consistency, which gives both Muddy Water and Rollout perfect accuracy. The issue was just being more unreliable than Mud-Slap, but I found in practice I was actually surviving for a while even with no accuracy drops while Salamence often used Flamethrower and Gardevoir threw in some Life Dews. My issue was just surviving after tera Rollout requiring dodges from that point on, which wouldn't be a problem with Shell Bell.
So in the end I actually dropped Muddy Water for the base game TM Icy Wind for speed control (outspeeding after 2 Winds), just relying on the locked in AI to survive the whole setup, and also getting more consistency on when I might die to stack cheers (which I used for a defense cheer). But I would still say Muddy Water is a somewhat viable option to potentially break through Salamence with too, even though it requires DLC, it could probably work with lesser AI comps.
Though either way, you do still have to wait to 65% time to actually start setting up Defense Curl and Belly Drum and staying buffed up for good one way or the other, whether by waiting or fainting, so there is some room for improvisation on that front still. But if you rely on accuracy drop dodges to stay alive, then you can also rely on guaranteed Muddy Water/Rollout hits with Zoom Lens or make use of other support AI like Bellibolt's paralysis, I suppose.
In this final attempt I ended up getting crit by Tera Blast, but put up 2 Icy Winds early, and animation time ended up letting Salamence get its buff clear on turn 3, so I set a manual defense cheer and died to preserve it. Then Salamence went into its 65% buff reset, so after I respawned I Defense Curled and outsped thanks to -2 speed from Icy Winds. At this point Salamence was at neutral Attack and so had physical Tera Blast active, hitting me to 312 HP (92 damage).
0 Atk Tera Flying Salamence Tera Blast (80 BP) vs. +1 252 HP / 0 Def Azumarill through Def Cheer: 80-96 (19.8 - 23.7%) -- possible 5HKO
I decided to go for a 2nd Defense Curl, got a Life Dew proc in the process, then went for Icy Wind 3 for tera charge while Salamence Flamethrowered. Another Tera Blast from there did about 70, though Salamence got another Moxie proc off killing Gardevoir in the same turn.
0+ SpA Tera Flying Salamence Flamethrower vs. 252 HP / 0 SpD Azumarill through Def Cheer: 31-37 (7.6 - 9.1%) -- possibly the worst move ever
0 Atk Tera Flying Salamence Tera Blast (80 BP) vs. +2 252 HP / 0 Def Azumarill through Def Cheer: 60-72 (14.8 - 17.8%) -- possible 6HKO
Then I went for Belly Drum, supported by Life Dew and a weak Flamethrower, and inputted Rollout and hoped all my 90s hit to keep me alive and end the battle. Salamence tried a couple Earthquakes in between, but I managed to survive thanks to large Rollout hits and healing.
+6 252+ Atk Huge Power Tera Rock Azumarill Rollout (240 BP) vs. 0 HP / 0 Def Tera Flying Salamence: 4574-5384 (46 - 54.2% of 30x hp boss) -- 53.1% chance to 2HKO
Salamence did get its scripted debuff reset and Dragon Dance in here, but it can't do anything with it on the free turn after the shield break, and Azumarill is free to land its final Rollout.
Technically this final hit was a 480 BP Rollout 4 and was entirely overkill, but when the raid boss is snowballing, sometimes all you can do is snowball right back at it.
+6 252+ Atk Huge Power Tera Rock Azumarill Rollout vs. 0 HP / 0 Def Tera Flying Salamence: 9150-10766 (92.1 - 108.4% of 30x hp boss) -- 50% chance to OHKO