Just as I said before, good vs. evil may be too simplistic. However, not having characters who are at least not wanting to torture everyone in a winning position makes the show more compelling.
Without the emphasis that Dany wants to free slaves, she's just a murderer and conqueror, the daughter of psychopaths. This distinction makes her deeds more compelling.
Whether the show runners want to admit it or not,they are telling a tale of good versus evil.
Jaime is evil for killig Ned Stark's men and crippling Bran, but he earns redemption through loss and heroic deeds. His deeds distance him from his comparatively cruel family.
Same deal with Tyrion. From a merciless family, shows mercy, so we like him.
Without characters who conduct themselves with a principle, whether they're killers or saints, the audience cannot root for anyone. What the show needs is a character who hates the Lannnisters, but also learned a lesson from the red wedding.