So, you just brushed off Azshara because she didn’t actually die twice, for Alleria, who also didn’t actually die twice and has far less to deal with old gods directly?
I think it’s far more likely that the person who the old god whispers refer to dying three times is the one that’s had two deaths related to the old god in question. The deaths are more than likely just symbolic, Azshara nearly died of drowning before selling herself to N’Zoth, and she was nearly (or was) freeing N’zoth to then be whisked off into the shadowy depths for who knows what.
My current speculation is that we’ll be fighting N’Azshara as the final boss of BfA, when we’ll kill her for the last time, unleashing the full might of the newly risen black empire