Read from the World of Warcraft client build files.
How Tranquil Bough Spaulders Compares
Who It Suits
Leather is the armor type Demon Hunter, Druid, Monk and Rogue wear. With Agility or Intellect, Tranquil Bough Spaulders suits Assassination, Outlaw and Subtlety Rogue; Brewmaster, Mistweaver and Windwalker Monk; Balance, Feral, Guardian and Restoration Druid; Havoc, Vengeance and Devourer Demon Hunter.
Transmog Sets
Tranquil Bough Spaulders is part of the transmog set Battlegear of the Dreadhide Stalker (Rogue, Monk, Druid and Demon Hunter only). The other 16 pieces:
Blizzard numbers items as they are created, so the named items next to ID 139072 (139067 to 139077) were usually added in the same batch as Tranquil Bough Spaulders: the same quest line, zone, vendor or reward set.