I searched the entire area repeatedly, over the course of several day/night cycles. There were none to be found, even on the peak in the Western part of the region, where they used to spawn in moderate numbers (and incidentally, mentioned by the contact themselves, as a source for these particular enemies). The one actual Archon I managed to find and pull from the Bog counted, but not the two I coaxed out of the Wolf's Throat, possibly because they were in the tunnel that passes under both regions.
Dropped this mission as needlessly annoying., especially for a repeatable, non-story mission.