I've only had to deal with PvP for one boss, Urtagh, the giant Infected Bantha during the Rakghoul Pandemic on Tatooine. I remember going into Outlaw's Den and spending more time killing pubs than fighting the boss. That being said it was interesting to do PvPvE. Given that that once you've killed NP 3 times for the Vehicle Achievement and gotten the Campaign Boots there isn't much of a reason to do him, I suspect people will stop ganking Nightmare Pilgrim Ops by the time 1.4 comes out.
Since anyone without the Buff dies when they fight NP, I suspect that they need to add something to make it more painful for griefers. I'd just set the fight so it was like a Duel where no one could interfere or like the Infernal Council in EV where you're abilities didn't work when you had the debuff. That way griefers could watch but not interfere. And after we were done killing NP we could pwn the griefers!