I can confirm again Scream Tail works. I was late to the party after travelling.
I refined my Scream Tai set for Feraligatr to:
Scream Tail @ SitrusBerry
252/0-/252+/0/0/4
Reflect
Noble Roar
Helping Hand
Sunny Day/Howl/Fake Tears
Light clay was dropped because psychic fangs breaks screens early. I still run with 152+ Def EVs (same scream tail), and it doesn’t really matter. Noble Roar is very useful to get rid of the Gatr’s SD boosts, since it is a fixed single SD. You can usually get at least one noble roar out before shields go up.
Sun is a bit more niche, but does a few things. Sun activates your own protosynthesis, it aids teammates where liquidation is the strongest move against them (eg Iron Hands, Sylveon), and it aids allied Koraidon via Orichalcum pulse after the sun runs out. Sun is not needed for every raid. You can alternatively run Howl or Fake Tears to support different attackers. Fake tears for the rare special attacker (I’ve seen Primarina and Sylveon), or Howl for Koraidon/Annihilape/etc. That move slot is kind of free.
Reflect T1 provides a lot of cover for your team, as people tend to take a lot of damage trying to handle +2 Gatr. Even if psychic fangs comes out after, Reflect into Noble Roar tends to help the team out more in the long term.
Scream Tail should never need Wish in raids. I didn’t even have full Def EVs, and never died.