The quests reference the recent past. While yes recent can mean a long time to dragons that guard time itself. Also it references the event that is shrouded having taken place at the nexus. The nexus is related to the blue dragonflight, and no blues were previously known to be major players in the war of the ancients. Except for of course the forging of the demon/dragon soul. The only thing in the quests that could be refering to the war of the ancients is the fact it has to do with Keepers of time, and the fact that it takes you to a spot that is related to the blue dragon flight.
Given the fact that it is steps taking place in the firelands raid, it is likely something that relates to the return of ragnoros instead of the war of the ancients. Blizzard wouldn't be so stupid as to create a legendary that has more to do with the next tier of content then the one you have to spend time doing just to experience the legendary quest chain.
Also it is hardly "spend a huge amount of money and get a legendary" since there is just as much collect steps as shadowmourne.