Your Death Strike crits Fel Spirit for 1019 damage.
Your Death Strike heals you for 2038.
At level 60. Maximum health is 5419.
I have limited experience playing Death Knights in PvP, but having fought them a bit on my Paladin, they seem nigh indestructible with a Blood build. Might of Mograine means my ~300 damage Death Strike hits turn into ~800 damage crits which heal me for 1600+ health which is about 30% of my maximum health.
Since I'm obviously playing a Death Knight now, I have no issues with Death Strike being so powerful, but my Paladin cringes as he pumps out 1,000 Flash of Lights that get interrupted, silenced and do zero damage to anyone.