If I remember rightly it was a small expansion set with no common cards in it- not sure why the rare % is so low tho- maybe there weren’t very many in that subset
Correct, Eldritch Moon, Oath of the Gatewatch, and Aether Revolt were all originally added into the packs of the block they were a part of, and no common rarity cards were added for any of those three sets. Additionally, masterpieces weren’t a thing until Kaladesh, so there wouldn’t be any in the Eldritch Moon packs either.
The loot chance for rare and mythic rare does seem reversed, however.
I’d say a majority of the peeps in my coalition who reported in reported pulling a rare, myself included. No way the 1.4 is correct. Mythic percentage seems right on though, gonna be a lot more piggies flying around after this event. Ohhh boy!