It was my theory that the Old Gods are corrupting the Dragonflights to sow chaos, drive a wedge between the mortal races, and cause a distraction before making their reappearance, given the depth to which this expansion goes into the lore of the Dragonflights, the Titans, and bringing up the Old Gods again after so long (which as far as I know were relegated to low-level dungeons in Azeroth before this). Deathwing goes crazy. Malygos goes crazy. If the theory about Nozdormu is correct, he's just yet another victim of their corruption.

"Nozdormu is difficult to defeat because of his ability to look into the corridors of time and repeat events if they do not progress as he feels they should. He is extremely wise and uses his insight to determine the best course of action before proceeding. Should this fail, he simply tries again as necessary, or uses his redo power to avoid the encounter entirely."

He sounds more like the 'Architect' from the Matrix put this way. Even the Architect knew the 'Neo' character needed to exist. The Architect was waiting, manipulating the outcomes, in order to find the 'one' that would 'save them all'. So the concept that Nozdormu is effectively engineering events to help him avoid death or achieve some other agenda is as plausible as any assumption at this point.

I think something else Wrath is doing well.. we're now CREATING lore, not living within the existing Lore that is the basis for the game. I think it's the players ultimately that will dictate what 'purpose' of the past lore served based on what we 'create' with what were given. Blizz gives is a base line, we fill in the peaks and valleys essentially.

Like one commenter has already said, and I concur, The phasing aspect of the game is going to bring us many many possibilities.