Skimming.... but in case it helps, I'm pretty sure GS kills shadow shield due to it having concealment.GS kills any spell that has concealment attached - in my experience.And that's why GS is dangerous in death magic territory - never cast it during combat (my personal rule at least). Also - I'd have to test, but I'm fairly sure the NEP from GS doesn't block horrid wilting. It's not until you have a negative energy immunity item attached outside of spells that it blocks negative damage spells. Again - I'm going off memory, and I get that wrong sometimes.
NEP doesn't matter against Horrid Wilting, as Horrid actually does magic damage (I know, wierd, huh?).
Tested the GS and SS up together and the SS repelled the spells. The troll, no matter what NPC I put GS on, saw through the GS.
You know that troll has probably been the cause of the most complaints regarding GS acting up. There might be something specifically wrong with that troll.
I don't know if its possible, but to prevent future problems and request for dt return, but maybe if the spall was taken out, this would definitly solved the problem?