The monster memory suggests goblin slavemasters should probably drop whips, yet as far as I know, they do not. Change it so that's one of the items they thematically drop, say, 10%-20% of the time. Tilt the drop rate heavily toward common whips to prevent abuse (and because goblins probably wouldn't be likely to have weapons of fantastic quality anyway). This'll give prospective whip-users a fairly reliable source for basic weaponry, as whips currently are pretty rare. There are already common, reliable sources for spears (spear traps/certain orcs), axes (gnolls), daggers (common orcs), bows/arrows (kobolds/barbarians), and pretty much every other basic weapon, but the only thing I'm aware of that reliably drops whips of any kind are balors (and a 1d3+3 weapon is a paltry prize for defeating one of those bad boys).