Yep, we did this in the way Zeitzbach mentioned. Open every chest during the mission, never build anything, let the minions walk alone, popping all the mobs through the way. The first one or two waves of minion will reach their target, but it’s not a problem. The purpose is that this way, all the mobs keeps respawning, and you can kill the ones close to Mellka repeatedly (the first 2 anchors plus the Varelsies in the tunnel).
Keep farming until around 40k score, then finish this part, aoe down all the mobs, and finish the mission normally. Be sure to get all the bonus score globes from the boss you can reach. We finished this way with gold medal, and 68k final score.
The main issue with this mission is simply that there is not enough score in the map. Only one boss spawns, and he drops bonus scores only when he’s killed. Either this map needs more mobs or any source of scores, or Gearbox have to lower the medal-requirements (around 40k total for silver, 50 for gold seems to be fine). Ideally both of it.