Ok, he's a dismembered head in a coma-tose state.
Feel better.
He might as well be dead, as Raiden has delivered him a fate worse than death.
Quan Chi could've used a doppleganger, but the more likely scenario is that Ed Boon wanted his favorite character of all time to finally get his vengeance for being wronged.
Thus, it's more likely that it was the real Quan Chi which was killed.
How do you expect Mileena to be brought back when Quan Chi and Shang Tsung the 2 sorcerers in MK are both dead?
Before you reply with your usual "Vogel said that Shang Tsung isn't dead," no he did not.
Vogel said that Shang Tsung wasn't inside of Sindel, but he never said that Shang Tsung didn't die.
Shang Tsung's curse forcibly decreases his lifespan, unless he takes the souls of others to replenish himself.
Shang Tsung's primary objective is to find an infinite source of souls on which to thrive indefinitely.
Should Tsung go on without souls, his body will rapidly age, wither, and eventually die (which is what happened to him in MK9).
Shao Kahn drained him of all the souls and he rapidly aged, withered and died.