It's still a horrible idea. It'd literally be extra (and bad) copies of life drain. Think about it.
Life drain: Blast an opponent's critter with it, and you gain life equal to its toughness, and since it doesn't *swing* at you the next turn, also gain life equal to its attack. Many times over, in fact. Furthermore, you can also point it at your opponent's *face*. By the time your opponent has a sizable critter on the board, you should have the corresponding darkness mana to blast said critter with a lifedrain.
And if you're running other colors (death): Why would you need any more life drain beyond the darkness card? Just gun for your opponent's head and race him with arsenic and deadly poison!