We got to the Mahjong Tiles on like round 7 but couldn't find any tiles and someone kept killing the zombie every round. We found our which was first (North) and guessed every round from then on. Of course the last possible combination starting with North is when it worked. They walked around the map for like an hour looking for tiles and arguing about which was the right one. Difficulty wise, I think our downs all added up to 5 so it was a good match.
Finished the EE back on friday, so there wasn't any extensive Mahjong Tile guides.