Also, there is a quest in Twilight Highlands with the Alexstraza vs Neltharion chain where Queen Al speaks of the Titans gifts and Neltharion (AKA Deathwing AKA Chinwing) responds with telling her about "the gifts of the new masters of Azeroth", clearly signifying he's but the grand puppet of an even larger force. And there is only one enemy that fits the anti-Titans superior force roll, especially considering the Cho'Gall & Deathwing lore.
Side-note: I roughly assume that while the air elementals help with DW, Ragnaros is mostly an opportunist & made a good "Molten Core was merely a setback" kinda boss, which would leave the water plain left (now scratched/delayed, maybe end-xpac bonus raid?) as all the elemental plains got imbalanced by Neltharion's actions. BWD was also a semi-revisit, although an attempt to tie it to the black/twilight drake stuff was made. One internet cookie to the first person to guess which boss it is