I would add some Removal, to get rid of threads that your creatures can't deal with. Maybe you should also look at Grimgrin-Corpseborne, since he has some nice synergies with Geralf's Messenger, and also the Gravecrawler, that's not featured in your dech, which it should. I don't really like the Goliath and the Ruinator, since you don't really have any enablers. I have also made a black/blue deck, with a little bit of a zombie team, feel free to look at it for inspiration and maybe give me some feedback: http://www.mtgvault.com/ViewDeck.aspx?DeckID=310872
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