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I kinda thought that Pale Green got the biggest boost but I suppose that's arguable. I updated the list.
Pfft... Broken Cisterns + Plagued with Diseases hurts you more. Negates all your draw abilities, and the combination of those two cards is enough to kill the two CBN draw heroes.
Broken Cisterns (perhaps with Holy Grail in the offense?) + PwD + Desolate Gateways in my heroless deck is able to decrease heroes by a total of like 6/12. Face of death is good too, but not as much fun.