These are the cards I recommend taking out, they either cost too much mana (Zombies in EDH kinda need to be quick, if you've got one or two out on turn two you're good to go. They'll start trying to remove the chump ones early) or don't have much in terms of abilities.
Corpse Connoisseur for Korlash, Heir to Blackblade (You're running mono black zombies, he's a must.)
Vengeful Pharaoh for Sorin Markov use his -3 ability to make target player's life total become 10. You can use it on yourself too if you're at 3 life
Severed Legion for Gravecrawler or Bloodghast for recursion
Highborn Ghoul for Stromgald Crusader (Zombie with Flying)
Polluted Dead for Adaptive Automaton (He's basically a general because he can +1/+1 ALL of your zombies)
Blackcleave Goblin for Festering Goblin (when he blocks, you can kill a 2/2 creature if it's attacking, put the -1/-1 counter on that creature)
Contagious Nim for Butcher Ghoul and not sure about where you play, most EDH players HATE infect. Too easy to win.
Gutless Ghoul for Gutless Ghoul, sac a creature it gets a +1/+1 COUNTER. Sac Bloodghast or Gravecrawler each turn.
Stinkweed Imp for Skirk Ridge Exhumer, discard a card (creature if you perfer, then reanimate) to spit out a token
Patriarch's Bidding for maybe Oversold Cemetery?
Syphon Mind for No Mercy
Promise of Power for Contamination, use with Bloodghast or Gravecrawler early game. Pretty much cripples all non-black decks so you kick ass
Sever the Bloodline for Ashes to Ashes, it's a 3 cost exile TWO target creatures from the game and you lose 5 life. Great deal.
Morality Shift for Victimize or No Rest for the Wicked.
Hope this list helps you out with your zombie EDH deck. Here's my current build if you want to look:
http://deckstats.net/decks/634/1337-dead-master-korlash-edh