Having seen Origins with multiple races and seen DA2 with human only I can honestly say i couldn't give a rats bottom which way they went in and of itself. Da2 was an inferior game with a superior story. Of all the things wrong with it, being forced to be human wasn't one of them, it was required for the story.
In origins the stories between the origins were not equal. And how the story of the main game wrapped into your origin was also not equal. As I recall the developers stated clearly that it was not easy to write and they couldn't do a lot of things they wanted because of the different origins.
The above said I think the "science" of taking story and putting it into a video game has progressed within bioware since origins. SWTOR although a different studio will have given bioware a LOT of experience on integrating varied back stories into other story elements. So I think either appraoch would have been right, it all depends on the story being told and they likely saw that x numbered of varied human backgrounds isn't that different from x number of varied racial backgrounds. and given that the story didn't require a very narrow origin like the Hawke story making the leap to different races wasn't a large issue.