I didn't realise you had to go in to *empty* systems to find Swoks/AI... that explains why I only encountered Swoks, and him just once, before I had much jump range. I almost always try to hit a yellow system, or at least a green to get the lay of the... space.
With how the NPC ships describe it 'ships in different regions may know different things' I'd actually thought that 'regions' meant the big 100x100 zones the galaxy is divided in to on the map. I hadn't thought of a 'distance to the core' thing, especially as you can start the Bottan mission way in to the Xanion space.
The band in which you can find these guys seems way too narrow at ~60 systems.
*Edit: Also, the mobile merchant who has the Xsotan artifact appears to be exceedingly rare. Is there a trick to finding this guy, or should I just sit AFK in a system and check if something has appeared every 15 minutes?