I think that if they make class quests, they should use the same item level scaling like they do in Challenge Modes. Part of the problem with the old class quests is that they just became completely trivial as soon as you out leveled them (not to mention, completely unnecessary as Blizz eventually put other methods for getting those rewards in game). If item level scaling was used, it would make the quests relevant for a lot longer. This would also add to the 'prestige' idea that you were talking about in a weekly marmot awhile back. Like Challenge Modes, the rewards are cosmetic and everyone doesn't NEED to have them to progress. Additionally, if someone were to start playing that class later on, and didn't get a chance to do the quest when it came out, they could still experience it closer to how it was originally meant to be done. Now, I know that with different spells and things in expansions, it might make the encounters play out a bit differently... but I think it would still be worthwhile.