HOTS getting its own story and characters is great, as this is the only game where we will see the Blizzard characters interact with each other. Speaking of Deckard, did you have a problem with him being added? You know, since he never displayed any form of combat ability in Diablo.
Same deal with Orphea by your logic. There are multiple characters from Starcraft, Warcraft, Diablo, and so on already…Stop being self-entitled just because Blizz decided to add an original character.