In the past, Blizzard Confirmed to us that we haven't seen a true titan yet, but now there is Ra-den. A Titan Keeper.
In the past, titanic watchers or keepers were just called "watchers", "keepers", "sentinels" or in rare cases, "titanic watchers". But in the Dungeon Journal, Ra-den is called a "Titan Keeper".
"Legend has it he found an ancient titan keeper guarding a miraculous device known as the Engine of Nalak'sha."
Does this mean he is a Titan? is this "titan keeper" thing his "race-class combination", like a "human mage" or an "orc warrior"? is Ra-den the First Titan to be revealed in-game?
he seems awefully powerful compared to the average watcher. remember those healthy watchers in uldum, which we beat in 5-man groups? well, ra-den is all beaten up, yet he's a hard-mode only raid boss. when lei shen took his heart, he gained special divine powers over lightning and wind. and when wrathion tells you to get lei shen's heart, he says it has the "powers of a god". true titans were called "gods" by lorewalker cho in his monologue about the thunder king and the mogu.
I think Ra-den is a titan