After every fight I spend hours trying to find the corpses in the grass. I usually look for the last 1-2 in vain. This is extremely annoying and frustrating. Is there a trick, because that can't be the point of the thing?

Early on in my playthrough, a dead enemy fell onto a large patch of very high grass and I can assure that I combed that patch and not locate his body. I think I simply just got better at making a mental note of where someone fell when they died and was able to find the bodies in later playthroughs. I know this isn't necessarily the answer you were looking for but you are not alone in this.

Later in the game it ist much better because of perks. But in the beginning it was horrible. Yes i tried to remember where they fell but often the physics throw them far away from the place they died.