Help! I was just picking up quests in Stranglethorn Vale when Nesingwary's Hired Gun shot me dead! I didn’t even touch him or attack—just standing there getting quests!
Greetings! Yes, Nesingwary guards are notorious for being neutral, and not friendly - a simple right mouse click while close enough will most likely end in a very sudden death.
As for your combat log, even tho it looks like the attack was completely unprompted, this is exactly how a combat log will look like in such a situation - when a low level player while in melee distance is right clicking (issuing autoattack order) on a high level npc, the level difference makes it incredibly unlikely that your autoattack actually lands. So, your autoattack did happen, but it just missed due to level difference and missed attacks by default do not show up in combat log.
In short, right clicking a neutral high level npc while being underleveled for a fight will probably result in an instant death.
Which is why i am to deny your ressurection.