From what I remember there was also a similar voice heard during the Battle for Undercity when Team Varimathras blasts off again, but that wasn't officially Sargeras or at least it was only speculated to be.
So, thoughts? Sounds fine to me but it kinda melds in with the whole rumbly low voice characters that are prevalent in the game.
Oh and of course the ToS trailer with Kil'Jaeden and Sargeras, but these are ingame voices.