Like I said, don't believe everything the Emperor's puppets tell you. They could have quite easily lied, if the Emperor was in fact dead it would be in their interests, leaking the information to anyone (especially to a newly appointed Emperor's Wrath, a position left open as the last Wrath betrayed the Emperor) would cause uproar and unrest within the Empire, and make the Sith Warriors role pointless. He'd just be the 'Wrath' of a dead guy.
Basically its the Lead Writer of SWTOR, who also wrote the JK storyline (and is the SW writer's boss) against the word of some imaginary in-game characters. Who are you going to believe? Personally I'd side with the guy who is writing the next chapter...
He does however hint that the Emperor has in fact survived his death, most likely as a lingering spirit.
EDIT: If you still disagree with me then how do you explain what Hall Hood said?
While this is true, one should remember, untill it's implemented in game, what the Lead Writer said can be changed.
"Yeah. That's what we originally intended, but we changed our mind."