I think I'd bitter with you're northern brewer and use willamette and cascade for flavor/aroma. If 1oz of nb isn't doing it from an IBU standpoint, I'd up the late additions to compensate. In my experience with using willamette for a hoppy beer is that it's "subtle". A lot goes a short way if that makes any sense. I've never paired cascade with 'em, but I think I'd go with 2:1 willamett:cascade.