I feel like I need to keep Blasphemous Act because it works so well as a reset button when things get too hectic, especially since it works in my favor when the Aristocrat is in play. And I feel like Dismember will be more useful in more situations than Altar's Reap will, especially since the only times I come out on top in card advantage is when I steal & sacrifice something with Conscripts or I sacrifice a Thatcher's token. Dismember lets me trigger morbid while negatively affecting my opponent more often than Altar's Reap does.
Altar's Reap IS a good card though, so I don't know.
http://i38.tinypic.com/2psgjyw.jpg What I say may be incomprehensible, but you can safely bet that it's an ironically condescending objection to your idiocy.