While the sound files that were datamined make it look like some characters might be dying (Lor'themar, Varyan i.e), I thought at first glance that those sound bites were there in case you failed the Siege/Escort or something.
Putting that aside, I think there might be some lore characters besides Garrosh & company that end up dying for each faction.
For the Alliance:
I really hope that Varian dies. He has too much screen time to the detriment of every other leader, and his character is a royal mess (specially the Lo'Gosh/Champion of Goldrinn bullshit).
For the Horde:
I know the world..of Warcraft will end first before Metzen decides it's time to kill Green Jesus, but huh, yeah, Thrall would be my favorite pick to die. If Garrosh kills Thrall he will become one of my favorites Orcs of all time, up there with his father.