Back in pre open beta there was a update that gave Unique dungeons and Time Machine Quest an worthwhile incentive to make people actually spam these dungeon more often then before, which were upgrade stones, but was later changed to make normal mobs outside these dungeon drop a little bit more stones then they normally would and just maybe it rare to see a stone drop in the unique dungeons.
Now I would to see this feat change back because it actually promotes players to do these dungeon more often instead of farming regular mobs which are needed for quests. Then it would actually make these PvE dungeon an decent zeni maker then before. Finally I just think it stupid that regular mobs have an higher drop rate then dungeon super mobs when it comes to stones
