I don't know about the Wishiwashi Trial TBH. :/ Both Rockruff and Litten are weak to Water types, and I just don't think they'd be able to do much considering the setting of that battle is supposedly a huge lake. And Popplio is too small to carry either one of them unless it evolves during the battle (assuming Ash and Lana are tag teaming, of course). Pikachu or Rowlet makes the most sense for Totem Wishiwashi IMO.Rowlet needs to do more, especially since a large appeal in him early on was that despite his clownishness he was actually pretty competent. I can see Litten or Rockruff having dibs for the next trial though, they haven't had one yet.
That said, I like his inactive time has at least been used showing him bonding with the rest of his teammates instead of just being a laughing stock. After the episodes he had with Popplio and Bounsweet I was worried he was going to end up another punching bag for the other Pokemon.
I could see them shining in the other two Trials, though.