My impression after a few hours of trying online and getting multiple kills:
The Double Team isn't anywhere as obnoxious as Bulk Up spam was, the raid rarely gets more than 2 up (very rarely 3) so counterplay isn't really necessary.
Intimidate & similar stuff at start is nice but not as mandatory as for Cinderace. Since you're not really going to get the oneshot, the boss will eventually get a debuff clear off. However, Mud-Shot spam is actually pretty nice as both Gunk Shot and Hydro Pump have significant miss chance on its own which just gets worse.
Since Greninja will do buff clear very early, setting up is actually quite safe, and once you have Iron Defense / Calm Mind / equivalent up you can tank hits relatively safely.
Stored Power is still the strat, however you're not really going to oneshot, rather going to take 2-3 shots since it's basically guaranteed for the shield to be up.
Stored Power users that look viable:
- Slowbro is still solid however it'll be eating Night Slash so there is the risk of crits thus you have to play a bit more conservative on HPs / Slack Off more often
- Slowking is basically budget Slowbro, does exactly the same thing so I mean if you have a shiny one you can use it
- Vaporeon is the new entry, Acid Armor + Calm Mind sets up defenses faster than Slowbro's Iron Defense + Nasty Plot, will be eating Gunk Shots instead of Night Slashes most of the time so you trade the crit chance for higher miss chance and risk of poison. You can also notably run Covert Cloak + Aqua Ring
Support mons that I've seen work
- Qwilfish. I mean, did you have any doubt? See post above for set and plan. Honestly I can't think of a better support at the moment.
- Clodsire provides an interesting combo of Mud-Shot, immunity to 2 attacks and Acid Spray. Can also use Yawn early to buy a few turns. However there is a very dangerous turn where the boss does the buff clear where you can eat a Hydro Pump and die horribly
- Slowking with Iron Defense can actually provide screens
- A frisky set I've seen twice and may be cooking up something is a Gallade set, probably specially defensive, which has Life Dew
- I've seen a couple Toxicroak but they didn't... really do anything. Yes it has Chilling Water, Acid Spray and resists everything + Dry Skin but I don't see it doing much more than all of the above.