I'm playing quite the odd game here, not killing anyone, but I have run into something strange..
For the first time ever I have used disintegrate weapon and armor to steal peoples stuff but I'm at loss of how they work. When I fought a dark brotherhood assassin I threw a whole bunch of disintegrate armor spells on him and they all hit him but after a while I just couldn't wait any longer so I killed him just to get rid of him and when I looked at his stuff, the only thing damaged was his cuirass and it had only been lowered some 150 points. I must have thrown more than a thousand points worth of disintegrate on him..

So. How does it work? Clearly not as I thought...