Very rarely are miles plus dollars awards worth it. They are generally capacity controlled - so people who aren't flexible in their travel dates can't use them, and people who are can often do better.
The real deals on northwest are out there, for example BOS-LAS was 98USD (114 all in).
But with the lack of miles awarded, these are dogs, especially with the partner mile program requiring that you earn WP miles to qualify. You could be losing, not just the mileage from the flight, but 5000 flight miles from partners as well.
Very costly.
My bottom line is: with award travel on NW as generous as it is - pay with just miles.