This item is acquired in-game. See its sources below.
A Rare Cloth Chest, item level 41, binds when picked up.
First seen in build 12.0.7.68887 (Midnight (patch 12.0.7)).
In the Appearances collection, Steamburst Robe is listed as Quest. Appearance ID: 21973. 3 other items wear the same appearance:
Read from the World of Warcraft client build files.
4 quests list Steamburst Robe among their rewards in Blizzard's quest data.
Foundry-Fired Plate Chestplate, 
Wildwood Wrangler Vest, 
Overgrowth Cutter VestFoundry-Fired Plate Chestplate, Wildwood Wrangler Vest, Overgrowth Cutter VestFoundry-Fired Plate Chestplate, Wildwood Wrangler Vest, Overgrowth Cutter VestFoundry-Fired Plate Chestplate, Wildwood Wrangler Vest, Overgrowth Cutter VestRead from the World of Warcraft client build files (JournalEncounterItem, JournalEncounterCreature, Achievement) and the Blizzard Game Data quest API.
Cloth is the armor type Mage, Priest and Warlock wear. With Intellect, Steamburst Robe suits Discipline, Holy and Shadow Priest; Arcane, Fire and Frost Mage; Affliction, Demonology and Destruction Warlock.
Built from the World of Warcraft client build files and recorded Auction House snapshots.
Steamburst Robe uses icon file 937862, which 18 other items also use. The 4 closest by item ID:
Auchenai Keeper Robe ID 112528 · Armor - Cloth · item level 42Slavebreaker Robes ID 112440 · Armor - Cloth · item level 39Podling Vineweave Robe ID 113154 · Armor - Cloth · item level 40 "The almost rubbery texture of this robe is the only sign it isn't made from traditional cloths."Firefly Robes ID 114254 · Armor - Cloth · item level 40Blizzard numbers items as they are created, so the named items next to ID 112607 (112598 to 112612) were usually added in the same batch as Steamburst Robe: the same quest line, zone, vendor or reward set.
Wildwood Wrangler Gauntlets ID 112598 · Armor - Mail · item level 41
Foundry-Fired Plate Legguards ID 112603 · Armor - Plate · item level 41
Steamburst Leggings ID 112604 · Armor - Cloth · item level 41
Wildwood Wrangler Leggings ID 112605 · Armor - Mail · item level 41
Overgrowth Cutter Breeches ID 112606 · Armor - Leather · item level 41
Overgrowth Cutter Spaulders ID 112608 · Armor - Leather · item level 40
Foundry-Fired Plate Shoulders ID 112609 · Armor - Plate · item level 40
Steamburst Mantle ID 112610 · Armor - Cloth · item level 40
Wildwood Wrangler Monnion ID 112611 · Armor - Mail · item level 40
Foundry-Fired Plate Girdle ID 112612 · Armor - Plate · item level 40The raw ItemSparse values for item 112607 in the current client build.
Read from the World of Warcraft client build files: Item, ItemSparse, Lock, Holidays, AreaTable and CollectableSourceVendor.
TheWoWDB