yeah, the fact he just lost his Perish Song user is a little concerning, considering it's the only reason he got past Mewtwo.
I agree the gauntlet battle is probably end of Season 2. He just kills off ANYONE good. He can't keep doing this. You can get away with off-meta Pokemon in this game, but they have to be well-synergized and covering each other's weaknesses.
Plus, uh, reading stuff like field read-outs helps too.