At a quick glance, there are 3 high CMC cards that I think could easily be swapped out for something cheaper [like a couple more vamps like the aforementioned Captivating Vampire]:
Boneyard Parley,
Hedonist's Trove and
Meteor Golem,
In Garruk's Wake isn't really that bad as at least its a boardwipe though if you have something cheaper CMC-wise, I'd play it instead;
Kindred Dominance fits a tribal deck just fine for instance. Still expensive, but cheaper CMC than Wake and cheaper $$-wise than
Toxic Deluge [which is fantastic btw, if you can afford it, buy one].
Unstable Obelisk is a potential replacement for the Golem, it can also get rid of a troublesome permanent [and can get lands too] but it is going to act as ramp before that point [and you could use more artifact ramp in here]. You could really use
Rakdos Signet and
Talisman of Indulgence as well.
Quag Sickness could easily be replaced by
Defile which is cheaper and does the same thing essentially though your
swamp count is a bit low to guarantee killing anything more than maybe 5 toughness when you need it. Maybe
Terminate is a better call here.
While
Geth, Lord of the Vault is a great card, not sure he's the best fit for the deck.
Necropolis Regent fits the vamp theme, slots in the same CMC and powers up your vamps.