They just confirmed that Sylvanas has been working with The Jailer since Edge of Night (after we “kill” the LK) and since Kael is in Rivenderth that means my guess that the “break” was when Wrath started appears to be correct.
Also they just confirmed that Chronicles is cannon from the Titan’s perslective, so there’s a lot that can be explored. Which confirms Pyromancer was right all along in that Chronicle is not the WoW Bible but an unreliable narrarator.