One thing to keep in mind about the other Doom’s.
Nysegard was the most heavily manned by D’Orc due to the Storm Lords, my guess is that the others had far fewer.
And if D’Orcus took say half? You might have only had a dozen or fewer D’Orcs with a largely mortal staff. If I were to guess, they would have hunkered down to protect.
I do think I should add something to the discovery of Doomalogues by Tom that a few of them had checked in, but by and large didn’t have the resources to aid much. For others, there might not have been that many shaman’s, maybe one or at most two, and if their contacts in Doom all died, they would not have had the links.
HOWEVER: You would think that there would be summoning stones for some of them in the Temple of Doom.