Yeah, this happened to me too. The first time I encountered necrosavants was in day 70 or so on Veteran Ironmode, during a caravan escort contract. There were 4 of them but was even worse since it was on a swamp map and my best soldiers had 65 close combat attack. I didn’t even try to save the caravan since it wasn’t even on my line of sight and I was deep into the mud, barely able to reposition my ranks. I missed countless skills and I had to retire when the whole party lost a man and tried to flee.