Depends from what perspective you look at. Fairly sure the whole Titan/Old God thing was pretty vague before.. WotLK? Cataclysm, maybe? Regardless, there was a point at which it was implied that C'thun took down a Titan with him and was thought to have perished but was just very weakened in early texts (Classic) from what I recall.
But that was obviously later changed. Not only were the Titans expanded upon, but also their methods of waging war, more or less. Later, it turned into stuff like Titan Keepers fighting Old Gods for them and the strongest Old God being essentially a gnat that Aman'thul ripped out of Azeroth.
Void Lords to me represent some level of DBZ-ification of WoW.