I was doing Pushing Forward and then Emergency Exit quests: first one with Wayward survivors helping attack the lizardmen in the camp, the second one where you rescue the scouts and escort the injured one back to the camp. In each case, when a mob was downed, the NPCs turned on my paladin merc (the regular one from Qeynos) and started attacking him. Luckily, it wasn't "in combat" so I was able to simply take off on my flying mount then drop back down and it was cleared. But how annoying! If I hadn't done the scout quest several times previously I'm sure I would have failed due to this issue.
I had similar issues with some npcs in a DOV zone. They attacked me just like the mobs did and chased me until they leashed.
That can happen in any zone with non-attackable NPCs and tank mercs. I remember having to do all of Guk with an NPC froglok following us around and beating on the tank. I always assumed it's to do with how the mercs' taunts work, that they're continually AOE taunting or something, and it affects white NPCs too, if they're close by while you and the merc are in combat. I've never had it happen with a non-tank merc.
