You'll need more turn-1 creatures. Pulse Tracker is a must, and Stromkirk Noble is also very nice (but costs some money). Remove stuff that are not vampires unless they're going to be really usable. Phyrexian Crusader is a bad card here because he wants to poison your enemy, while other creatures want to kill by damage. Another thing to note is that you must run more copies of certain cards, running singletons will make your game pretty inconsistent.
Also, Blade of the Bloodchief is cool.

for one drops, Pulse Tracker and Vampire Lacerator, as well as Viscera Seer are amazing. you can sac in repsonse tho any creature dying or getting exiled. get yourself some Bloodghast to make seer even more pimp. haven't played much with Shadow Alley Denizen but i see some potential. Blade of the Bloodchief seems to be a bit disruptive to the synergy of nocturnus, so would Stromkirk Noble, although he would be a good side board guy against humans. Deathrite Shaman is out of hsi element in here i believe. more Blood Artist! And consider Kalastria Highborn

and i feel Crypt Ghast should only really go into a mono black or control deck. If you like extort, i would check out Thrull Parasite. you can start extorting MUCH earlier, especially if you lower your average CMC

and gatekeeper was awsome until Tragic Slip came along. I dont like him too much because i he's a bit situational. his mana cost with the kicker is a bit strict for two colors as well.

to those complaining about the color, look at the land in this deck. its basically mono-black. im working on it tho, things like the Isochron Scepter dont really belong now that i realize it cant copy sorceries. and im not such a fan of lightning bolt either, i want Blightning instead so its black for Vampire Nocturnus. but tragic slip isnt a problem really...if someone kills malakar, then i just killed a creature and made them discard a card for 3. still not a bad move.

oh i meant having gatekeeper in your deck as removal. Tragic slip would be better, although both would be nice. Gatekeeper kicked, then tragic slip. Blightning is best in sideboard card against control. what did you mean about the land? are you aware that they are colorless?

i see you have Rakdos's Return mainboard. maybe switch with Blightning and have return for those longer matchups?