Who It Suits
Leather is the armor type Demon Hunter, Druid, Monk and Rogue wear. With Agility or Intellect, Harmonious Bearer's Gauntlets 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
Harmonious Bearer's Gauntlets is part of the transmog set Garb of the Harmonious (Rogue, Monk, Druid and Demon Hunter only), which the Appearances collection lists in 2 versions. The other 8 pieces:
Built from the World of Warcraft client build files and recorded Auction House snapshots.