Eh, parry hasting has been more or less adjusted for boss encounters, you won't find parry gibbing on bosses where parry gibbing would actually matter like Patchwerk. It's been balanced for. There is a blue post stating that, if you want to dig through trackers.
That being said, the problem you'll run into is primarily threat generation as a DW Frost tank. I have ran with DW tanks in better gear than me (as 2h tanker), and the primary problem is threat not parry-hasting.
Right now, there is no reliable source of data, EJ included, for the definitive conclusion for DKs simply because we are under-documented for being a new class. What I can tell you is that the cookie cutter Frost builds you see will be better than the Unholy builds right now with the changes to BA and UA once the new patch hits live.