I have a relatively recent save with a hero from the Fortress faction, leading a legion of dwarves and dendroids. I'll try a battle against him with a small group of vampires; maybe it will work. I couldn't manage to clone a hero with dwarves and goblins.

By the way, I also encountered the possibility of killing the orange Fhure before he visits the blue tent and blocking a lot of dungeons in the orange zone, but I decided not to do that.

Added 5 minutes later
What's the plan for killing Orrin? Theoretically, he one-shots any of our stacks, regardless of their size. Hit and run? Or do you have enough power to take him down in the first round?