There are five goblin bands in the Hinterlands, but there used to be six until Deverin Hosk wiped out the Bonegrinders. It seems unlikely that they could possibly have lived closer to Sandpoint than the Birdcrunchers, who are in the Westernmost part of Devil's Platter, so why would Deverin choose them to exterminate?
I'm guessing that they were doing the most raiding and hurting commerce the most. This suggests to me that they either used to live on Ahsen/Ashen Rise or else in the area around Leb's Tors, and routinely hit caravans. The latter works a little better for my plots.
Anyone have any other thoughts on this?
... so why would Deverin choose them to exterminate?
You could just go for the 'bitter old ranger' route... they killed his father, and he prepared them to die. Inigo Deverin?
Now he's 'retired' again, and just runs his normal life being a stablemaster, which was his original calling until the goblins intervened.