Why are halflings mutation resistant? Is there something in their blood?
Are the lizard-races resistant as well (as they were the elder races that taught manipulation of raw chaos (magic) to the elv3s)?
..and still going: elves should be less "crazy", dwarfs shouldn't be resistant to disease/poison (because their environment doesn't have those kinds of things in relation to what humans, for example, have to live in), and what's the point of halflings being resistant to anything?
What in these creatures' physiology makes it so?
This all just feels a little too "D&D" where it's based on their statistics, but not in relation to how these creatures would have evolved and adapted over the past 6000 years.