Epic drops have reached 505 and will no longer be tracked.
Sentinel drop rates from completed data sets:
Common: 1.6%
Rare: 1.4%
Ultra-Rare: 1.2%
Epic: 0.6%
Sentinel drop rates from incomplete data sets:
Legendary: 2.8%
Mythic: 4.5%
Still odd that the Epic rate is so much lower, but my guess is the data set just wasn’t big enough. Legendary/Mythic will continue to drop as more data comes in.