I don't think that's that reasonable a fear... But if you do worry about that, then you should be voting for the Reckoner -- the one that is can hide itself -- rather than the Retaliator.
If you're that worried about And Then Suddenly, Bloodthirsters! to the point you'd want to keep a hero from the boss fight, vote for the option that uses the Rangerstrike combo warmachine.
Me, I don't think that's going to happen. Especially not for the opening shot. They might send a ton of people at the warmachine's position after they see it give Kholek the whallop of a lifetime, and that's what the Runesmiths and Huskarls are probably there for. But by then it'll be too late for the daemons, because it will have already fired the shot at Kholek. Though it'll probably be firing more shots at Kholek and/or his Dragon Ogre escort even after the first big one, so, it'd still remain useful and good. I mean. A warmachine is always good of course.
This is a period when the Chaos Gods could deploy literal divisions of Greater Daemons lead by Exalted Greater Daemons. Now, I don't think there's any chance we'll face that, as they have bigger fish to fry, like Aenaerion defending Caledor while he created the Vortex, Grimnir marching north and leaving the Road of Skulls behind, and the Slann defending the temple cities, but I really wouldn't want to assume that they couldn't shake a single Greater Daemon loose at this point.
I think we need to maximise our chances of a knock-out punch on Khorek while also having insurance against something like this happening.
As a side note, I expect that the climax of this battle will be at the same moment Grimnir reaches the end of his road and Caledor activates the Great Vortex.
No thanks, don't want to, I'm fine.
Ok. My answer then is:
I don't neglect that fact. Like... the "ancient records" that the sentence talks about, one of such records is the one they start with right afterward; the -1500 IC one with the pastoral tribe that disappeared into the forests. So before -1500 IC, we aren't as sure of what was happening, so if proto-proto-Empire peoples and events might have ended up then being important a thousand years later... Can't really be sure of what happened before -1500, so move on to the part where we're both more sure and where it starts talking about the Empire-tribes directly. (And -1500 was when the Time of Woes hit with its earthquakes. With "During this period, the records of many strongholds are lost or disrupted. Even the Great Book of Grudges in Karaz-a-Karak falls silent during this period", being said.) I just decide to get on to the bit where it starts with the tribes that would form some of the Empire's tribes, specifically.
Anyway. I don't ignore the starting sentences. Rather, I was instead deciding not to take it as an open-ended "nobody knows when humanity entered the Old World" = "well since we don't know for sure, for all we know a good deal of them were there all along!" -_- i.e. Deciding not to take it as an opportunity to go "Well it doesn't say so it could be anything." And then deciding to move on to look at what it said about the tribes. Not the pastoral ones of -1500 (which are "stamped in the ancient Dwarf runes no outsider is allowed to see" Just a normal mention of how the Dwarf language is secret and private. Though amusing seeing it's secretiveness get brought up here and now.) but the ones that are noted as sounding similar to the Empire.
Ancient records spanning centuries that are used as the basis for dwarven scholars work is more than one IC source, is my point. There are then the other runes carved in Black Fire Pass, and the contemporary 'dwarven lays'
The pastoral ones are those we have most detail about, as it happens. There is a record of one of the first dwarven contact with humans. We know the date, in -1,492 IC, and IC they know the circumstances of the encounter in great detail, as the dwarven High King at the time had it recorded, including analysis of the craftsmanship of their tools and their camp, along, I think with their religious artifacts. This is the basis on which he named them Umgi, as the quality of the work was shoddy.
Now, importantly, until only relatively before this point, the dwarves still had surface settlements, and before then they were moving around across the Old World prosecuting the War of Vengeance. There's just not very much time for significant unnoticed human presence in the northern Old World to develop. Some could have been there that the dwarves (and elves, back when they were friends with the dwarves) didn't find but there wouldn't be large numbers of them.
But I think we've exhausted this topic.
