Random realization I had in the car, spurred by Absoloot going through the thread: holy shit, Thorgrim is going to be devastated when he gets the report on Dum, because when Vlag's flow returned to the Karaz Ankor, so did Dum's. So he would have had hope, just as the thread did, that the impossible had happened and his people were alive and well and maintaining their Hold in the face of... well, all the everything. He would have carried that secret hope for weeks, waiting for any news of the Expedition, believing that maybe Belegar's Zhufokri might manage yet another miracle.
And then he's going to get the news that Dum may not have held out at all, but committed acts the Karaz Ankor finds unconscionable, and that'll hurt all the more for the weeks that he had reason to believe they were there to be saved. The Norse Dwarves all over again, that's what it will feel like to him.
I'm fine with any of the top 4, but now I find myself wanting more than before that we get Loremaster-at-large or Waystones, so that we have a chance to ever talk to him about this. Because damn, I believe axiomatically that knowledge is better than ignorance, but sometimes knowledge sucks.