We have some DK changes going live, as Blizzard have fixed the 
Festering Scythe bug. They had to change the way the spell works entirely. It’s now a buff on the Death Knight instead of a debuff on the target, but the issues should be fixed.
We have recently sent out a large hotfix to address the issues for Unholy that came with the 12.0.5 update. Part of this change was updating Festering Scythe to be a buff on the player that increases their disease tick rate instead of a debuff on the target. The underlying issue here was proving to be problematic for a number of reasons and we felt like this would be the safest approach for now.
We will continue to monitor any potential issues and we appreciate the patience and understanding.