Read from the World of Warcraft client build files.
How Arcane Defender's Pauldrons Compares
Who It Suits
Plate is the armor type Death Knight, Paladin and Warrior wear. With Strength or Intellect, Arcane Defender's Pauldrons suits Arms, Fury and Protection Warrior; Holy, Protection and Retribution Paladin; Blood, Frost and Unholy Death Knight.
Transmog Sets
Arcane Defender's Pauldrons is part of the transmog set Leyline Defender's Sunplate Armor (Warrior, Paladin and Death Knight only). The other 16 pieces:
Items Numbered Next to Arcane Defender's Pauldrons
Blizzard numbers items as they are created, so the named items next to ID 134272 (134267 to 134279) were usually added in the same batch as Arcane Defender's Pauldrons: the same quest line, zone, vendor or reward set.