I've had the opposite experience. In the past nine months, I've been able to redeem my NW miles for the following:

- IAH-ATL-CDG-MRU RT x 2 in AF Biz Class 330 days out on DL/AF at the standard award rates
- PHL-IAH-YWG-PHL RT x 2 in Y with less than 30 days advance on NW at the standard award rates
- PHL-DTW-HNL RT with less than two weeks advance on CO at the standard award rate
- Five long haul one-way FC upgrades on NW at the standard award rates

I'm probably just lucky, but I've never once had a problem redeeming my NW miles this past year and my dates and times haven't been flexible for any of those trips.

By contrast it has become nearly impossible to redeem my DL miles at a standard rate and CO continues to be useless in that regard as well. At least I have no CO miles anymore and only about 35k DL miles left. I've burned all but 9k of my NW miles but they really just build up again so damn fast.

peace,
~Ben~