There are two roaming placeholders, and they are always "a discordling surveyor". The spawn time does not seem to be consistent. It seems to be anywhere from 12 minutes to 16 minutes. Since this is a roaming spawn, the spawn point appears to be anywhere along its roaming path.
If you use "Brewalls Maps", the approximate spawn and roaming location is marked on the map.
Took me about 10 hours of camping. The named guy spawned prolly once for every 8 or so placeholders. He finally dropped my lute on about the 12th named kill.
Hope this helps.
Edited, Oct 7th 2020 2:46pm by JMo