Yep, I swear it wasn't there initially when I posted though, might have missed it or might have been updated shortly after to clarify :/.
Yea I thought it'd be 20 initially as well (so same timing as heroic - push big add big enough, and you can skip the spawning tentacles), but it does read as 20% more dmg = 4.8% per.
As for blood DK, we don't have any Huntorz - I'm sure 1x will be more than fine, but having the grip reduced from 25 to 15 sec is a fairly big deal :P.