I've seen it stated many times on these forums that Dungeon Scaling is not in effect when entering a quest on elite.
I proffer the following evidence in favor of Dungeon Scaling's existence, albeit to a diminished degree, in Elite difficulty missions:
In a Normal difficulty mission, solo, Vicious always deals 1 damage to the attacking player with the weapon equipped, instead of the stated 1-3.
In a Normal difficulty mission, with a group of six players, Vicious deals the full 1-3 damage to the player.
In an elite difficulty mission, solo, Vicious deals 1 or 2 damage to the attacking player, but never three. In hours of play today doing lower level missions for favor, across hundreds of attacks, I never saw a single 3.
Has it ever been explicitly stated by a developer that Elite is unaffected by scaling?