Undocumented and ham-fisted nerf to Deathbringer Blood DK has been discovered on live with a sluggish rotational change rather than number tuning.
Deathbringer BDK now no longer gets a stack of exterminate when casting reapers mark. This is a measly 3% damage nerf that is unlikely to affect DB Blood's standing amongst the tanks.
While the power budget effects will be small, this change represents a severe rotational damper put on by blizzard for no good reason. Any blood player would have gladly taken a 3% tuning nerf on exterminate over this change. It makes the rotation feel far more awkward, sharply reduces the fluency of aggro in mythic+, and makes it more difficult to obtain max stacks of reapers mark before the buff's expiration. But most importantly, it makes Deathbringer feel *way* less fun to play
Edit: It is now documented. Still cringe