Put it this way. It is completely your choice to decide the stat build of your character, because that is what truly makes your NS different from every other NS out there.
But what I can do is give you the information you need to make an informed decision. Firstly, forget str, it just gives you like the ability to carry more weight in your inv. Dex only gives NS crit, like we need anymore of that lol, even without setting any stats ur almost perma-critting anyway.
Here comes the two major choices. Int adds dmg of course, and cons adds hp and mp. It is your choice and to ur preference to find if you like pure int for max dmg, pure cons gives up some att, but gets you a nice bit of hp/mp or a perfect combination for you. Anyway, don;t be afraid to experiment, Crean can reset your stats for a very small fee, so feel free to experiment.