I've gotten 10 "curious item" drops in about 3.5 hours of playing today. I don't know if the drop rate improved or if it was because I changed what I was doing, i.e., walking very very slowly while outside town guard zones, pretty much sticking to the roads as much as possible because it takes longer that way. This means going from Minoc to Skara Brae takes about 40-45 minutes with about 35 ambushers along the way and from Minoc to Trinsic takes about 50 minutes with about 52 ambushers along the way. I have been using a tamer who drags along a greater dragon.
Since this started, I've gotten 5 amulets, 3 phylacteries, 2 goblets, 2 incense, 1 scourge, 1 wand, and 1 gorget. Still need the map, tome, boline, and stole to get a complete set on the shard where I've been doing this so far. I'm pretty sure that I inadvertently pitched a scourge the first day because it came from an orc and I thought it was one of the whips some of the orcs crop. I suspect I might have overlooked a wand on the first or second day too.