@en9nhcet
Ok as much as everyone “knows in their heart” Dawnbrnger is really “supposed to be” a Mythic weapon. Sirrian is actually referring to MUCH weaker weapons such as Dragon Oak, or Serve and Protect as a Mythical class weapons in the 1.0.9 notes. Of course Epic rarity is more appropriate for that set of weapons.
As for Dawnbringer the fact of its enormous cost to forge, and unique Tri-color mana the miss coded “Legendary” Hero weapon Dawnbring should be corrected to Mythic.
@Jainus is right restating that both Legendary (and Mythic) troops are not allowed in Arena…
Finally,
If only someone created a thread about this before perhaps it would have been looked at. /s