All of the NPCs were amazing, and while I was tempted to hand out my vote to Kristen, JP, or Philippe, I suspect they are very much used to praise from the player base as favored NPCs. I could see the experience in their interactions at game that spoke louder than words that they have been doing this (and doing it well) for a while.
Justin however as I understand it is fairly new to NPCing, and I could tell that he was giving it absolutely everything he had, and Justin people noticed. My vote is for Justin this event.