In vermintide 2 they served as a purpose of taking risk for improved rewards and those rewards could always translate to high quality loot even if Ranalds Gift decided to shove you a middle finger in your face.
In darktide they just serve the purpose of completing your weeklies, besides that you are taking unnecessary risks for meaningless rewards you get some extra dockets and xp and thats it.
Fatshark should review the rewards change the dockets and xp for actual weapon/curio and even cosmetics depending on the difficulty you did with grims or scriptures
Personally Iād would had scrapped the system and made alternative secondary objectives, given that darktide is using the same map for different objectives why not include and option where you have to do an extra optional mission (raid ,strike, assassination) in a more contained form? Only would require to open an extra wing on the map, I know the issue would be connecting with the main objective later or not just let the players deal with the attrition in order to return to the main objective giving thats a risk and reward move.