I dont have any advertisement, my adblocker does not discover anything there. Sorry if you are having problems.1) the upload site is a MESS, try using tinypic.com instead of showing us REALLY small pic covered by huge advertisement..
2) that screen only shows last 5 sources of damage. You can't just count that and say that you were at 50% HP.. I even had a screen where all listed damages were under 30 HP and I died.. because I was stuck on ground after being knocked down and CC-break wasn't responding
I died in a sec3) Disintegrate should work when hit by shock damage under 20 (or is it 25?)% hp. That means you must have been bellow that threshold and just not notice it.
4) I think Disintegrate proc OVERRIDES the damage it procs from, because it's in every way superior to it - there's not reason to list another hit when the target's dead anyway, it would just slow down the system with another calculation. Instead of let's say hitting 100 dmg with a shock enchant, you get ~15x+ more damage instead.
Disintegration should only proc for high damage when the target is being hit by lightning element damage when below 25% health. 25% health is generally what the game refers to as low health. For the record, it is possible for disintegration to proc on non low health targets but it only deals 1 damage in those circumstances.
Disintegration also does not overwrite the damage that procs it; at least not in any of the addons that show your damage done through the API. I doubt the death recap would be different but no one other than ZOS knows for sure.
On a side note, it is interesting to note that disintegration can proc even for non-sorcerer characters if they are using evil hunter combined with lightning damage. I have seen it proc multiple times when I was using crushing shock + evil hunter against daedric and undead mobs.