Let me start off by saying this is not a "please nerf the difficulty post" I have no problem with the difficulty the way it is. It's simply a post about NPC behavior. NPC's need a new move other than to constantly try to flank the player. At higher difficulties (especially legendary) it makes the NPC's so aggressive they constantly try to walk right up next to you, and sometimes right around you, in order to find a flanking position even when there isnt one available. In my opinion this is why the NPC's can be so aggressive at times. NPC's only know how to do 2 things, flank or take cover. The problem I have with that is it seems like they are programmed to flank 90% of the time and to take cover 10% of the time.
As a suggested fix for this, I propose adding a 3rd move to NPC behavior. "Take cover when taking heavy damage". This would stop them from trying to constantly flank, and would also eliminate them face tanking the player.
For me this is the best part of the game, NPCs that are constantly running back and forth, trying to find a spot that suits them best. But they always fail to find one and end up dead. While they are running most of them aren't shooting and thus become easy targets. When they try and come closer, also one of my favorites, simply switch to my shotgun and they are toast at close range. For me the worst ones are those that run of and go play hide and seek, then at times they hit you even tho there are huge objects between the player and the NPC.
While doing the Capitol Mission today I did however notice that some actually do have some new moves. When running they run forward, back, forward, and back again at lightning speeds. Not sure why and how but they do 180s on a dime and at ridiculous speed. Then I saw this gunner running and in one huge leap he jumped up and into cover. I checked were he went I my character had to climb first in order to get up whereas the NPC appeared to be flying. I think they should rename fractions, it seems they all turned into Olympic champions, despite some of them carrying heavy gear.
The flanking is easy to stop when you start the fight in good spot where it is hard for them to move besides you. In other cases try and find a spot to fall back so it takes longer for NPCs to get to you. This usually makes them run in a straight line and again they become easy targets. But when playing legendary, NPCs don't need to use cover, they have tank-skin so there is no need to take cover, they wear it.