Just played Nightmare Conflict at the Carrock and it was epic. Took my powerful two doomed decks (Glorfindel, Grima, Aragorn & Eomer, Legolas, Imrahil). I built up my forces for 5 rounds and then dropped both deck's threat to starting level (via Aragorn & Desperate Alliance) and then took down the four nasty trolls. It was not easy.
I defeated all four unique trolls and then set up stage 3 with Rob/Bob alone with a Savage Hill Troll and Hill Troll (I already killed all of them but these two). It was very interesting and funny because I actually used Hill Troll's forced effect (raise threat from excess damage) to my advantage by forcing the Grima deck to threat out after it attacked so that Rob/Bob did leave the side of the Eomer deck and make a second attack. This forced Rob/Bob to stay where he was and allowed me to kill it with Gandalf (sneak attack), Imrahil, Legolas, and Eomer who was attacking for 7 by himself (Grave Cairn gave him another 2 attack from a fallen Westfold Outrider). It was really close (next turn I would have been slaughtered by all three trolls!).
I really, really enjoyed my experience. I have never had to think so much and take so much time to plan and strategize my every move, especially the final round in having to intentionally sacrifice one player in order to win. Thank you FFG for putting this nightmare set together. It really made for an exhausting challenge. I am looking forward to more nightmare decks in the future. I just wish these came with the original game so we don't have to spend all this money for them. I am thankful for what they did with easy mode, but I wish they could do the same for nightmare mode (put a red color ring on ones to put in for nightmare challenge).