I just refuse to believe these endings as real.

Well, the "bad" ending is, just as any other ending when your party just dies, or when you choose to kill Emperor too early. But the good one... It SHOULD be just one step to the REAL ending. There should be something about Karlach's saving, Gale's quest to divinity (well, you can have that if he is your main character) or githyanki rebellion. The game is just not complete without these.