Nah, you can cheese it.
The setup: Have Cecily stand to the left or right of the door. Have Grey Rat stand 2 spaces below the door. You might want to use the Rally skill to position Cecily. Do the mine trick to kill 1 or 2 dudes.
The execution: Lure enemies in 1 at a time, standing on the wall opposite to Cecily. Whack the dude with a wooden club immediately after Cecily attacks and avoid attacking while they're stunned. The more on point your timing, the less often Cecily will get hit. Save between kills so that you can reroll the save before Cecily gets downed.
Even if the timer counts down, the newly spawned enemies will kinda explore the map. After killing like 4-6 enemies, the path should be clear enough to leave.