Yeah, I believe when I moved my little crafting building farther away from the NW city the NPCs started spawning again in that area. The respawn radius for NPCs seems to be much different (larger) then the no build radius or the respawn radius for trees and rocks/iron. Trees and rocks were respawning near my base, but NPCs that should have spawned in the distant horizon were being blocked.
I don't know what that was about because I have a small outpost near the pirate ship that is a lot closer to a small NPC camp and they respawn just fine.
Maybe it just had to do with some location information for my base during and update that messed things up and once I destroyed it things opened up.
Right now I have a couple bases at the following locations:
1 Large Base in the middle of the map in the G4 area
1 Medium Crafting/Trall base in the NW in the C6 area
1 hut up on a hill in the south with a bed and a box in the G2 area, this JIC I'm helping people in the south I have a place to bind my respawn point for when I eventually walk off a cliff. I can destroy this now that I've added people to my clan, they have larger bases in the south that I can use.
1 small house and wheel North of the Pirate Ship for capturing Thrall up there.
I made sure that when I built my places there was no other bases in eye site of these, but if someone find they want to build here, I have no issues moving stuff around, though I'd rather not kill off the first 2 bases, I've put a lot of time into those. I also don't have any Fencing or walls up to block people out, so feel free to come on in. I've taken down ALL my non crafting NPCs at all my bases. Fighter/Archer NPC's are a pain to everyone else if you are in an area that people have to walk through to get to stuff (Story NPCs etc).