You know, one thing about the Great Old Ones and the whole cultist-issue attached, they are not nearly as terribly dangerous as they look at first glance, even in Lovecrafts own works.
I don't mean them personally, and I don't have to mean them personally, because they don't come to earth.
I mean the whole cults and minions thing. It looks impressive at first, but let's go through some actual Mythos-stories.
Call of Cthulhu: Cult is wide-spread, but at every turn they are met with actual force they crumple easily (both the cult in the swamps of Luisianna and the ship near the island rising from the sea). They are badly organised and for the most parts the followers are primitive and crazy.
Shadow over Insmouth: Deep Ones followers are broken up the moment the forces of the state are mobilized. They did manage to take over a small town, and even that took time and direct help from the Deep Ones, the cult was no big deal at all. The south-sea version of the cult was even purged by their non-evil native neighbours and we never heard of any retaliation hitting those.
Dunwich Horror: No cult at all, just a small family that couldn't even keep their Necronomicon in a sufficiently good state to call Yogg-Sototh with the incantations within. The second-to-last "horror" got killed by dogs while trying to steal from a library, the real Horror of Dunwhich was driven back by three old professors and then smote by Yogg himself when he dared call on his father.
The Case of Charles Dexter Ward: The wannabe-necromancer being the main-villain in this piece got first killed by an angry mob in the flashback-part of the story, then send to closed institution because he couldn't believably play the person whose identity he stole, then killed by the doctor-protagonist, while an angry spirit he tried to call up killed his necromancer-colleagues over the world.
Those where some of the most famous stories, I think?
So in every case the bad guys seem terrible and are described as such by Lovecrafts prose, but when faced with actual resistance of either mundane or mythical, they break down. It's all paper-tigers.
I think it's not unreasonable to think that the cult here in Qohor (even the supernatural threats behind it, even boosted by our more accessible magic from D&D) are not as bad as first descriptions might imply, and that we can deal with it.
I really hope
@DragonParadox doesn't feel the need to make his eldritch monsters live up to the false hype some of them later got and instead keeps Qohor as a reasonable challenge, not a bottomless pit our efforts have to be poured into for turns on end.
