I did sort of use that technique but oddly enough I didn't think to rest in the passageway. I guess that was because those poltergeists are so numerous on the way down the path that I thought maybe they were respawning all the time and I figured I might have to get to the bottom of the path to get past them. Up until that point in the game I hadn't encountered monsters with anything like the same frequency which is why I thought they were respawning.But that doesn't seem to be how the game works, it seems there is a finite number of monsters in every area that only respawns after a month or so.
All the same - you must have had quite a bit of patience to beat that dungeon at level 11! Even at level 30, I had to rest my party a lot to beat it.
