I'm having the same problem. It extends to the entire game, because I went back to Defiance Bay after that, and there thugs didn't attack either. Even weirder: I reloaded a game from Searing falls before I entered that cave - start of the map - and mobs that attacked before, now did nothing. A reload from before I entered Searing Falls seamed to work at first, but when I entered that cave again the bug also appeared again.