So, I was doing the Shadowseer hunt, and scouring Subterra for Black Orbs, and I had very good luck with the treasure chests, nailing a Ribbon, an Ultima Blade, a Circlet, a Dueling Mask, and Lordly Robes. I don't think I've ever had such good fortune down there in any previous playthrough.
I didn't have quite as good luck in the Great Crystal or the hidden Henne Mines. In GC, I got a sage's ring instead of Excalibur, but I already had two. The Zodiac Escutcheon/ Brave Suit chest didn't generate after all the running back and forth to get there. In the Henne Mines, no real good chests. Gr.