You are right about the epic chest thing. I had to wait two days (and it seems I was lucky), and I had no time for the collect 60 epic cards quest. Relying on chance only for a quest does not make for a good game.
I still liked this quest because I got two Aztecs, a couple of those Hell's Angels (one was an epic girl), and I got one of those black cougars as well. I had one Aztec from the gem chest in the shop area before, but she was just the one who does the power of nature, and she is still far too weak to actually use. I have been using the earth girls from the dungeon who have been getting very strong over the course of this game due to level ups.