So there is this bug. I stood against Mirage and fought her, Korg was present, but then I decided to try the other way around but ultimately went back with the former decision, and now Korg is bugged. His journal said he fought me with Orgram and was taken back to camp to be "broken". The Orc War quest's journal still said I fought Mirage, then now Korg is no where to be found, and I don't have any saves before this.
Dunno if this will help, but this is my personal saves collection. The most recent save is right before going to the camp confront Mirage (good path for her demon children).