Diablo III Plot Analysis Article at Gamasutra

Josh Bycer over at Gamasutra has posted a lengthy article on what he considers to be the storytelling faults in Blizzard's Diablo III. As I put quite a bit of time into the game myself, I find myself nodding my head with much of what he has to say.
2. RetCon:

Multi- part stories can be tricky to design, as the writer needs to keep the plot moving. A common pitfall that can happen is the writer going back over previous plot points to reintroduce them into the story with a different meaning. The hero finds out that he was the chosen one all along but didn't know it until this very moment for example.

Or: the hero's best friend actually hated them the entire time and was just using the hero and now wants to back-stab them. This point reeks of bad writing and the audience can collectively groan when the writer uses this point.

Diablo 3 features a very confusing retcon in the form of the Nephalem. According to the game, these are the children of angels and demons from a long time ago. They supposedly have super human powers and are set up as the game's version of the chosen one.

This doesn't make sense, considering how the world of Diablo was set up. In previous games, the heroes have always been regular humans who were trained in supernatural professions, and they were able to save the world. Were they really Nephalem the entire time? And if so, why did no one mention this at all over the last two games?
Did Blizzard's reach exceed its grasp when it came to Diablo III's storyline, or are the flaws in the plot merely a reflection of apathy towards the series' narrative?