I forget which one exactly, and I won't do all the work for you, but I can help point you in the right direction. Planet Destiny uploaded a video about it in the weeks before TTK was released. The videos main purpose (or rather the first half of the video) discussed the announcement that there would be three versions of the raid. I believe it was all Like Smith that said this, but, again, it's been a while. Although he is a much more credible source than Deej, as he a actually has a large part in handling the game.