Heinous Ritual modifier places juiced up daemonhost (DH) that will get agitated as it notices players closing within certain distance.
With how vertical levels are all connected in the Hourglass missions, traversing through these terrains often create aggro from the enemies that normally shouldn’t get aggro-ed in other walled up corridor maps like Hab Dreyko, etc
Being in an elevator does not prevent these DH from “spotting” you, especially when their placements are deliberately too close to an elevator’s upward path.
In Refinery Delta, the first medicae station is usually hot mess with hordes and boss triggers sitting on top of it, and the DH in hangar below “sees” you while you are still ascending in an elevator to get to a medicae area. Once you arrive at this area, it will get more “agitated” and starts filling the bar faster, because it can see you making a lot of noise and spectacles through the fences; note that you can also shoot through and be shot through these fences.
Maybe a solution is to shoot the psykers from above? Have few players to stand and shoot at the rather tanky psykers that can chew through multiple plasma and bolter rounds to the head and survive require quite some time. Except, the situtation around there does not really give time and space for it, as it will be flooded with horde and or boss(es)
Maybe make all these walls solid wall rather than fences and it may help with the line of sight issue that lets hexbound DH to see you in an elevator? or just simply review various positions of the rituals and adjust them so they aren’t designed to simply end the game no matter how good the players are.