In Wrath of the Lich King it is item level 251 and requires level 80. In MoP Classic it is item level 251, requires level 80 and sells to vendors for 1c.
Read from the World of Warcraft client build files.
How Relentless Gladiator's Wyrmhide Helm Compares
Who It Suits
Leather is the armor type Demon Hunter, Druid, Monk and Rogue wear. With Agility or Intellect, Relentless Gladiator's Wyrmhide Helm suits Assassination, Outlaw and Subtlety Rogue; Brewmaster, Mistweaver and Windwalker Monk; Balance, Feral, Guardian and Restoration Druid; Havoc, Vengeance and Devourer Demon Hunter.
Items Numbered Next to Relentless Gladiator's Wyrmhide Helm
Blizzard numbers items as they are created, so the named items next to ID 41328 (41322 to 41334) were usually added in the same batch as Relentless Gladiator's Wyrmhide Helm: the same quest line, zone, vendor or reward set.