There are different forms of PvP. Isolating it to areas of the map doesn't make them desolate: a lack of enjoyable PvP play is what deters people from bothering to visit those areas.
Having players that act as bandits or haunt highways isn't necessarily Griefing. I really don't want to discuss that right now, psychology and RPG design and whatnot, but I do agree that the DR needs to be evaluated for such kinds of character presence.
What do some of the Citadel Library books reveal about those which choose to dwell in the DR? If you suppose that pathological tormentors could take up residence there, which is a possibility, and that other persons nevertheless manage to escape it, which also seems to be so, then obviously there is something about the DR which keeps stronger ones from settling in a niche that allows them easy prey.
Maybe later I'll share my insights, but I really don't believe that anyone developing PS would care.