I haven't thought about this idea completely, but a karma system can actually be maintained in a magical society. I mean actual karma, the way Hindus and Buddhists think about. What goes around, comes around. Violate it badly enough and the universe will make an exception just to get you out of the way. As another commentor put it, somebody would have tried to protect another while they were being avara-kedavra'ed, earlier than lily protecting Harry. But voldemort's karma credit really ran out. So, whoopsie, there goes the body. But of course, he had his horcruxes.

But if making people realize that we have to wake up in this hostile universe is one of the goals of this fic, the above wouldn't be true in HP&MOR.

Another speculation, maybe true prophecies only come when there are serious thresholds crossed.