Er, DC has a 30yd range? You can use it to pick up adds or when you can't be in melee range of the boss.
Don't compare DC to titans grip, those abilities have nothing in common. Compare it to Heroic Strike.
DC has been the main RP spender for blood in WotLK, and the "Sudden Doom" talent was a blood talent.
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Why? Why would you rather have a completely new ability, unrelated to anything, rather than DC, which has been part of the DK forever?