In comparison with The Pitt's Trog Hordes, for your worry about more spawn affect economy of loot.
Trog is the typical example of fast moving hard hitting melee machine. Hard hitting because my Courier typically wear Naughty Nightwear fighting.
back to topic of the horde: They can move fast then jump on my courier fighting melee. VERY dangerous because at their range guns are pointing elsewhere. And that's with their huge size of savage or brute. If it's outdoor like the roof with 360o vision, I dont know where they will hit me.
++ IF it's small size of shielded aliens, that would be even harder to shoot because gun barrel will poke outside of their bodies.
++ MOjave's Bitter Spring Recreation Office, the room with 5 giant rats. More Spawns (and maybe other mods) up the number to 10. They swarm all over my trio. Sure, at 25HP apiece, that's just one burst kill but the number is OVERWHELMING. even counting that small office full of table.
I usually pick a good small location (like a doorway, or small corridor/walkway), firing up the auto axe and wait for them to move into my weapon. If they're far away, I throw a grenade in their direction to get their attention.
Conclusion: More Spawn work in great effect (as in threatening player) in Pitt. I used chems all the time to raise my defense, throw grenades to get their attention, and if not for the need of using auto axe to kill, would waste bullets on such poor target. Fighting trog is a losing proposal in term of loot vs expended resource.