Drop rates for the keys were really high some hours ago. I got lots of Mithril keys in the loot and was able to open the Mithril chest like 20-25 times per 30 minutes (gil + loot made approx. 50k gil in that time). Also got several Electrum keys. SE apparently lowered the drop rates (http://forum.square-enix.com/ffxiv/t...l=1#post374564), I don't know how it changed.