No, once you finish the game on one difficulty it opens up an initially locked higher difficulty. You also open up other classes and races to play that way as well.
Yeah, me too. I didn’t want to burn out on it before release (but I still do have something like 90 hours in it). It really is one of the best tactical games I’ve ever played. And not only is the tactical layer great, I really like how the world map and events are handled too. It’s a great total package and deserves to sell really well, imo.