An interesting one, no point in trying to loop with just refund, since single enemies are berserkers.
Best option is to bring as many NP batteries as posible and just nuke with a ST Servant, the power of the Event CE is more than enough really.
Keep in mind that the Chargers themselves doesn’t really matter who they are, AKA Waver+Skadi or Reines+Waver or just Skadi+Reines. Any combination works.
Also It’s better that you DPS has a battery of their own.