Despite having Scale Shot as its Dragon STAB and TM drop, Dragonite will prefer to OHKO and Extreme Speed most things at +6. However, there is one AI that will guarantee picking Scale Shot, and that is Drifblim thanks to being immune to both other attacks. This allows any physical mon to deal more reliable damage, and what makes this Azumarill solo somewhat possible in time (affording an extra death).
Because there's barely any window to buff up and inflict debuffs without taking damage, Azumarill's gameplan is to wait 3 minutes for both resets to pass (and not get hit by T0 Hurricane) and start spamming Mud-Slap while Dragonite is still setting up Dragon Dance, though this may be counterproductive for hitting Scale Shots but you don't need to go to -6. Note while playing in group mode you auto input every 60 seconds, so I prefer to just lose on the initial game to lock in AI. A +6 Extreme Speed will OHKO (still likely with 1.5x Defense) and you can't really mitigate it fast enough, so I just went for BrightPowder and Substitute to buy as many turns as I could much like Azurill against Sceptile. I hit 3 initial Mud-Slaps (Dragon Dance, ESpeed miss, Dragon Dance) and died to the next hit.
After respawning, I substituted and he missed but hit the next attack afterwards. I went to -5, substituted again, heal cheered, Belly Drummed, and started tera Play Roughing for the rest of the fight. At this point Dragonite was only around -2 defense (ending at -3), but it was still doing great damage to the shield with 3 hits to break and a 2HKO after (with some misses).
In the final 2 turns, Dragonite was only at -3 defense.