Patch 4.1.0 (26-Apr-2011): Death Strike self-healing no longer generates threat.
Hotfix (2009-04-21): "Death Strike will now heal the Death Knight for 5% of his or her maximum health per disease on the target, up to a maximum of 15%. [1]"
Hotfix (2009-04-17): "The healing a Death Knight receives from damage done by Death Strike has been reduced. [1]"
Healing changed to 5% of maximum health + 5% per disease, up to a maximum of 15% with 2 or more diseases.
Patch 3.1.0 (14-Apr-2009): Increased damage to 75% of weapon damage (up from 60%), reduced healing by 20% to 80% of damage dealt + 40% per disease (down from 100% of damage dealt + 50% per disease).