Here are more thoughts on the adversity roll. I decided this should be separate from yesterday's post, since I'm going to be talking about potential applications of the roll instead of the most likely interpretation of the rules as written.
From what little is said about the adversity roll, it appears to be meant to represent the body's resistance to natural damage, as opposed to the character's luck and determination to avoid unnatural effects, or unnaturally escape extreme natural effects like poison. Thus, character level has no effect on adversity rolls: some things are just going to cause significant real injury no matter how lucky the character is.
We might want to expand on this idea to add a simple injury system on top of the luck-based hit point system: a significant fall (more than twice the character's height) has a chance of breaking bones, reducing the character's movement to the overloaded (3") movement rate until healed. If we use the "2d6 => Con" rule instead of percentile or d20-based mechanics, we can even avoid the use of an additional roll: if damage is equal to or greater than Con, the character is physically injured.
We could also use an adversity roll to determine if a dead body is intact and thus subject to Raise Dead. Some forms of attack always render a corpse unraisable, as could aimed shots or post-mortem dismemberment; but if your comrade is swept over a waterfall and dies, an adversity roll determines whether the body is too battered to be raised.