I feel bad for Frost DK's who don't have Unholy leggos to or the desire to switch. However, this was pretty obvious this was coming. The loss of rime tier bonus pretty much looked like the end of the world to me, several weeks ago then they topped it off with a nerf to the BR relic, for good measure.
So far, parses look exactly how I imagined them. Frost on bottom and Unholy near the top / upper middle. This is what happens when you basically lose on-demand aoe, scale like shit, and have a weak toolkit.