Codger, if you're reading this I'd really appreciate it if you could be a little more detailed in your explanation of how you do these types of missions.
Well, as I said, I take my own ship (small ship, I use a Viper MKIV) and approach the base low and fast (so they won't spot me coming in if they are already on the ground). I land about 400m outside the base because scavs won't come out that far. Usually I get there before the scavs, and so I sit in my ship and watch them get dropped. I use the camera suite to see where they land. Then I wait a few moments to see if they've spotted me in my ship (usually not, but if they come running towards me and attack my ship, I just relocate to the far side of the base, staying low so they lose track of me).
Once I know the scavs are in place and patrolling the base (I can check again on the camera suite if needed), then I exit my ship and approach the base. If I'm in the Dominator suit I have an Executioner, Intimidator, and Tormentor as weapons (sniper, shotgun, pistol). If I'm in the Maverick suit because I need the arc cutter, then I'll only have the Intimidator and Tormentor. I watch my radar as I approach, turn on my shield, turn on night vision if it's dark (not required by any means, but I like it), and try to locate the scavs and see where they are patrolling. If I see one off by themselves I take them out with the sniper rifle or pistol. Audio Masking helps a lot here. If you don't have that you have to relocate immediately after firing because the other scavs will hear the shot and start looking for you.
I continue to whittle them down one by one as best I can. If I'm seen and they get alerted, I switch to the shotgun and run around behind cover and over roofs, whatever it takes to get near one scav who's away from the others. Two shots of the shotgun from point blank and they are dead, except for some higher level ones who take 3 shots. Don't miss. Then run away again.
I never let myself get caught out in the open, I'm always behind cover. If my shields go down, I run away, dodging behind cover until they come back up. I never engage more than 2 scavs at a time, and prefer one. I run around until they reposition in such a way that I can do that. If you pay attention to the radar it's pretty easy to isolate them.
The rest is just experience and having a good feel for how the guns perform and how well my shields hold. You really don't want to get hit when your shields are down, ever.
That's fairly detailed, I hope? Is that the kind of mission you meant?