I thought I had a 3500 run, but apparently not, and I’m not willing to grind this again just for the extra 50 points. I will settle for 3450.
For 3000+, terrain is not needed, and in some cases it might actually be better to not use it, because it frees you to run any 2 supports that you choose. Ideally one tank / healer, and the other a debuffer or utility unit. Flinchers like Eevee or Snorlax for Supereffective boost could work, but unfortunately Marshall’s sync is fighting type, so these 2 units will not survive a sync.
Sabrina’s Reflect helps us survive the enemy sync very easily, and then her healing lets Blastoise survive long enough to get a 3rd sync. I save Luminous Love for post-sync which might look like it doesn’t make any sense, but if Marshall uses a trainer move instead of an attack, we can actually skip 3 turns (Luminous Love + Blue’s Adrenaline) which lets us get our second sync a bit earlier. The main damage output comes from the second and third syncs. The first sync doesn’t need to crit, but the second does. You also need to hit the post-sync timing after sync 2 in order to fit in a 3rd sync in. Overall, it’s not as good as having Musharna on the team, but it’s still viable depending on the context.
One thing I’m looking out for is a consistent accuracy debuffer which can activate Hide and Sync. May could work, but Muddy Water takes up too much gauge and doesn’t provide anything else for the team. Clemont is simply too weak to survive a sync, and provides very little value otherwise.