I was in Reaper's March and came across the NPC Werewolves that infect you, so I put out a zone wide call to tell everyone they were up and where. Several players were on their way when a bot train of Sorcerers that was running around the area slaughtering tigers blew through and killed them. The players on the way of course didn't make it in time and my understanding is those NPCs do not respawn.
It is past time they and the Bloodfiend NPCs were made unkillable. Both to protect from something like that bot train and from jerk players who kill them out of spite.
The purpose of art is washing the dust of daily life off our souls. ~Pablo Picasso