Regrettably, HDR isn't as capable as on iOS as it only takes one physical shot, and applies very strong shadow pulling afterwards. This also means that, if you expose the highlights and/or manually apply negative exposure compensation before shooting and, then, in pp, just pull the shadows (and, if you did apply negative exposure compensation during shooting, compensate it too), you'll have exactly the same image as with the HDR mode of the stock Camera app.
I can post a very detailed explanation of this if there's interest - I've made tons of experiments with the N4 camera.