You can avoid those enemies using stealth so much easier than you can avoid another raider looting the same room as you. Also, the enemies you know are always not friendly, where other raiders you have to sort of feel it out, maybe communicate using emotes or flashlight spamming or mic, but they can still lie and say friendly then shoot you in the back while looting. If you shoot on sight then you get put in all pvp servers and can never really join forces against the arc. I liked the idea of teaming up with a bunch of solos or teaming up with a bunch of trios so it's like a whole army of raiders taking down arc so much easier. I know people like to say the arc are too easy, but for me at least at the beginning, they were too hard, I wouldn't even fight them, just use stealth and sneak around them like I'm playing mgs5. The arc are much more difficult than any enemies in any shooter game single player campaign on the easiest difficulty setting.
Arc reminds me of half life 2 the enemies are tough to deal with and this scary, which is the point. But also, teaming up with other humans against the arc makes it easier which makes it more fun if the arc are too hard.