Was on this toon yesterday and was constaintly dieing. Toon was a level 20 attacking level 19-20 NPCs on leveling quests. I did notice that every time i did a lighting attack, that it didn't do a thing to the NPCs health at all. And that includes all lighting attacks. My companion did a little damage but died also just before I did. These NPCs were just regular NPCs, no Elites. I got heals for other players, but only one for me, what good It did. That and a medpack didn't do a thing.
Sounds like PvP to me