Locational damage multipliers are a thing that reduces the damage if you hit different body parts on enemies. Most enemy types take reduced ranged damage from hitting their arms and legs.
The intention is clear, hitting extremities is not meant to be as good as centre-mass or headshots.
The problem is most enemy stances have them holding their arms in-front of their body acting as a shield to ranged fire. This gets really bad when you have cloth wearing troopers surviving plasma or bolter rounds because it hit their gun arm.
Melee weapons have a mechanic where if their sweep travels through multiple bodyparts, it chooses the best one [In some cases it does the opposite]. This was also how it worked in vermintide; you could shoot through the back of monsters and hit the head with the right aim.
Something needs to be done.