It's the kind of thing that normally makes me pretty sad too, when the main characters die. In this case, it didn't trouble me. Still made me sad, but it didn't trouble me. Both of them essentially gave everything that they had, both had some truly epic final moments, and they died doing what was right. What more can you ask for in a hero? Also, it neatly sidestepped any separation of the two, or the loss of Vin's extra powers, or a power disparity between the two.