Yeah, I had toyed with the idea of W/R, but decided to remove the Goblin Bombardment for Blasting Station at one additional generic mana, it does the same thing and doesn't have me squabling for the proper mana combo. The only way I can think of to improve this combo would be to add more scry or card drawing.
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Is there a particular reason you chose Last Grasp over Grasp of Darkness? They cost the same since you're running mono-black and Grasp of Darkness is -4/-4.