Wow, this three-tier award system that DL now offers and NW will be adopting staring January 15th sucks. I figured the bad news would be that DL would be allocating fewer and fewer seats at the "low" tier award pricing level. While DL is probably doing exactly that, it's even worse than I feared:
the published tier rates appear to be entirely illusory in that the published "low" level is only a floor, not a ceiling, and the actual price of a "low" tier award appears to vastly exceed the published mileage cost. 
Please see
here for my findings.
I guess I better scramble to burn my half-a-million-mile WorldPerks balance. What's unfortunate is that the January 14th drop-dead date for redeeming mileage under the existing WorldPerks paradigm precludes award redemptions over next year's Christmas and New Year's holiday period given the 330-day window.