SeaGtGruff wrote: »I think "sweeper" would be overland quest bosses, not the mobs and mini-boss that fall from the sky-- those are considered to be "incursions" and drop the type of golden plunder skull you'd get from a dolmen.
With public dungeons, it seems like the bosses may or may not drop plunder skulls depending on how long it's been since the last plunder skull-- that is, they have a cooldown. If you're basically "farming" bosses in a public dungeon and are in a group that can farm the bosses quickly, you might have to kill several bosses before you get another plunder skull.