I have something like 40%+ and I've found... a lot of set items and I seem to find them more frequently from monsters than I do bosses. I have an abundant amount of uniques and I usually find a gold item every few mobs I kill. It might also help that I have +61 to all skills and +21 more to enhanced perception resulting in a total of like level 83 enhanced perception.
I've also noticed that if you have high MF and high EP the bosse's (some of them) chests give an equivalent drop as the boss does. So when I kill my dragon I essentially get 3 drops haha (it's the dragon near the Grundwal or whatever it's called teleporter which Ascaron, for some reason, won't let me activate anymore).