horizon-zero-dawn
When I am in a quest sometime I go searching for some healing plants, or I hide from some robots (not far away I am still near the quest area).
I noticed when I get back to the original area, the robots that I have killed have re-spawned – it's like I am repeating the mission again.
Why is it that if I leave the quest area for a minute, the robots/humans that I have killed re-spawn? Is this normal?
My favorite strategy that blends stealth with action is to create a mess of tripwires between you and your prey while utilizing Concentration and Tearblast arrows to stealthily take out opponents from afar.
From what I can tell, setting tripwires (though very loud) is perceived as silent by Machines. By that I mean you can place them literally on top of/through Machines and they won't have any idea who did it. Even when walking into tripwires, Machines typically will not find you if you're hiding behind rocks or in tall grass.
Once you've effectively set up a no-man's-land of crisscrossing tripwires in every direction (bear in mind that the maximum placeable at any time is 16), you can try getting headshots/destroying components of Machines. Another way to set these up is to basically fence a group of Machines by using tripwires. Electric will immobilize them and allow you to get a Critical Hit on however many were affected, while Blast wires will cause massive damage (and likely remove components).
If you are able to use them (they are on the Sharpshot bows), Tearblast arrows will do little to no damage, but will quickly remove the components of Machines (which effectively incapacitates them) and allow you to take them down more easily. Concentration will also help you hit these components and weak spots by slowing down time and zooming in, so it's very helpful for this.
If the Machine you're hunting notices you, they will most likely charge. At this point, they're extremely likely to run into at least one wire of your giant tripwire trap and then begin the process of stumbling into every other tripwire you've set. If this hasn't killed your prey yet, it should have come very close to doing so, at which point, you can use your weapon of choice to finish them off.
The handholds are slightly past where the campfire is, near the crevasse with the creek coming out through it.
Video:
You can also get up there by fast traveling to the campfire. If you got close enough to discover the campfire, you can fast travel to it without having saved at it previously. I've done this a few times with similar campfires that were at the top of a climb.
Best Answer
It seems like it depends on the quest. In most cases, they seem to never respawn, but in at least one quest that I encountered (find out more about the mysterious woman at the site where Olin mentioned), they respawn, like you said, even just being a building away. It is very frustrating, to the point that it did seem like perhaps bug.