This writ involves a little back and forth - from the camp, to a separate dock area, back to the camp, and then to the tower. The key to enter the tower is one-use only - the door cannot be opened from the inside.
This means if anyone is left behind, or you find you've not killed all you need (before realising you've gone past a point of no return), you need to do the Deep Kiln run again, including getting the key, into the tower, and so on. The fact the area is thick with spawns also means that any transition can put you in the middle of two to three sets of sets of spawns at once, and as you do need to go back and forth - you will likely have respawns during this time.
If possible, moving spawns away from the transitions, or spreading them out a little would help with the latter, or finding a way to go from the docks to the tower, without having to go back through the camp itself would prevent that issue. The tower door should probably also be openable from inside, to avoid locking people out