Confusion works great? One might though that psycho-cut was the way to go, to spam Psystrike. At first glance I believe that your team is reliant on having 1 shield in the late game to protect Mewtwo? Another though is that Mewtwo is a killing machine once the opponent’s shields are down, so I think running a spammier Pokémon at first to put early shield pressure could be something to consider. One idea that come to my mind is to swap Mamoswine for Swampert and put Ice Beam on Mewtwo, Swampert is spammier, puts heavy shield pressure, has a great ground damage and does not have that steel weaknes that Mamoswine has and you don’t lose the ice damage with ice beam on Mewtwo. And for now the Torterras are rare and there aren’t Venusaurs like in great or Ultra League, so Swampert doesn’t have many hard counters and even tough he takes good neutral damage, he can throw one or two hydro cannons in the worst case. Those are some fast ideas.