The corpse despawning is horrible, with everything at max, I snipe one guy from like 100m away and by the time I get there the body and loot are gone. Or I see 2 supermutants attacking a trader, I engage from range and the melee one charges me. I kill him point blank, then go get the one still on the trader. When I'm done, the first mutant is gone. It's not like there are so many bodies that the game has to delete some for performance reasons.
But of course the bodies that it HAS to remove, they stay there for weeks. The ghouls I killed in Sunshine Tidings a few weeks ago? Yep, still there. Empty bodies not despawning, and no idle settler would even think of removing the stinking bodies.
This despawning issue is actually affecting gameplay and fun. I climbed on top of a highway ramp, I crept to the border overlooking a raider camp. It would have been nice to use the sneaky sniping skills I have been developing in this character to rain death on them from above. But I already lost a body to an untimely despawn while I was getting on top of that ramp, I am sure that the kills I will make from above will despawn by the time I get there too. It's a shame we can't use those skills.