Read from the World of Warcraft client build files (JournalEncounterItem, JournalEncounterCreature, Achievement) and the Blizzard Game Data quest API.
How Slayer's Shoulderpads Compares
Who It Suits
Leather is the armor type Demon Hunter, Druid, Monk and Rogue wear. With Agility or Intellect, Slayer's Shoulderpads 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
Slayer's Shoulderpads is part of the transmog set Slayer's Armor (Rogue only). The other 9 pieces:
Built from the World of Warcraft client build files and recorded Auction House snapshots.
Where Slayer's Shoulderpads Fits
Other Items Named Slayer's Shoulderpads
1 other item in the current build is also called Slayer's Shoulderpads. Same-name entries are usually a different rank, faction, quest stage or reward track of the same object.
Blizzard numbers items as they are created, so the named items next to ID 150563 (150558 to 150568) were usually added in the same batch as Slayer's Shoulderpads: the same quest line, zone, vendor or reward set.