So I am really enjoying the base building portion of the game, my settlement has finally been invaded and I noticed that the settlers assigned to guard posts do in fact not guard their post at all. I was expecting there to be some sort of cover animation where they shoot from behind the walls of their guard post but they just run away from it like imbeciles. In fact unless the post is on ground level and very easily accessible (NPCs seem to have a ferociously difficult time traversing stairs it seems) they just stand there completely incapacitated. This really seems to limit design choices when building a settlement where the defences are functional :/, not just aesthetically pleasing.
Of course this may just be general bugginess experienced from my limited time with the game but it is rather unfortunate nonetheless.