So, as everybody knows, there are many loot caves used to farm engrams.
As much as I farm as well, I think it is pretty cheap because players just free farm engrams and get them for doing nothing.
So, as a proposed fix, I feel that bungie should increase the npc's threshold for damage. Like how they increase the damage npc's can take during a random event when you are lvl 25 and they are lvl 5.
I don't mean right away, as there could be just some harmless killing involved in that area, but over a prolonged time they should increase once a certain amount of enemies have been killed.
So once a certain amount of enemies in that specific spawn area have been killed, let's say, 100 times constantly, they gained increased resistance but stay at the same level (So the lvl 5 acts as a lvl 10 or 15, and increases again once another cap has been met).