Yeah, N. Korea.....
presents a kind of special case and my opinion is that such extremes are best left out of a general theory. In the end it is China's problem anyway-by which I mean they are the only ones in a position to actually effect any real improvement. All the well intentioned round tables and summits, etc. are good showmanship from a diplomatic perspective but it might be better to just state our carrot(we are everyone's friend when it comes to commercial relations) and our stick (use nuclear weapons and there will be no more N. Korea for anyone to bother with), and then shut up. leave the door open but don't make much effort to beg them in for tea.
I don't put Iran in the same club. Iran, for all its domestic awfulness is not the Howard Hughes of the world community that N. Korea is. They want to play on the world stage and they know that there are rules involved in that. Like any slightly doctrinaire regime they will push things as far as they can, but that may not be nearly as far as the more hysterical factions in the neo-con community believe. And they already know that a number of nukes are already pointing at them.