Well, if you'd like some realism...
Sometimes it happens that the next group that goes in has very little idea about what happened to the ones that went in before them save for "They went there before you." Maybe the same goes for the daimons? The Elders might have gone to Daimon group A and said "Go to the human world." Group A loses contact with the Netherworld Elders, so they tell group B "Group A disappeared. You're up next. Go."
I am pretty sure this stuff happens in real life more often that we might want to believe. For example, when I took over the duties of my predecessor at work, I was told what I had to do but nothing about what went on before that.
Another take on it is maybe the daimons don't care about humans at all and would give about as much thought to their actions against them as a human would to the many bacteria they kill by washing their hands.
