I haven't officially made it to MooShu yet, but I'm out of quests. Legit Quests:
To Locate Big Ben Cat for the Prospector. Where's Big Ben? I need to locate the Eight Yardbird in Helgrid Warren. I don't think I have access to that area yet. The last message I got said I should let rising heroes take care of stuff in Grizzelheim. Use Story of Earl in Northguard. I couldn't get into the throne room.
Possibly from a stolen ride to Mooshu: Make two Seal of the Seraphim (I don't have the recipe.) From MooShu: Collect History of Mooshu From MooShu: Defeat Death Soldiers and Collect Stolen Message
It sounds to me like you should be in Marleybone, probably talking to either Watson or Sherlock Bones. Big Ben is the final dungeon in Marleybone, after you complete each of the Counterweights.
GrizzleHeim is a parralel world, meaning that you get access to certain areas at certain levels, provided you completed all the main quests in the previous area, and you get access to the throne room once you complete I believe the first 3 areas of grizzleheim.
For the Big Ben cat, that's the final dungeon in Marleybone. The cat is behind a set of crates to the left, so go up a certain floors, and you'll find him.
As for Mooshu, you can get the crafting recipe from Toshio. The history book quest, look to see where they're located at, and use your quest helper when needed. The Death Soliders are in I believe the village of sorrow, but you have to keep fighting them until you get the stolen message.