Hello there, I have some suggestions:

To protect yourself from graveyard hate, you could play cards that give you hexproof, such as Sigarda, Heron's Grace, Leyline of Sanctity, or Aegis of the Gods.

Mazirek, Kraul Death Priest is great in a deck with a heavy sacrifice theme. It is a bit of a nombo with Mikaeus, the Unhallowed, however.

Yahenni, Undying Partisan is a strong card overall in EDH, and is also a free sacrifice outlet if you need one.

Have you tried running any of the dredge cards like Golgari Grave-Troll, Dakmor Salvage and Life from the Loam. These can help get your graveyard nice and large. Also I run The Gitrog Monster in my deck because he is extremely powerful with dredge because it could allow you to draw 2 cards a turn plus put some of your creatures into your graveyard. Also Duplicant is a great card to get rid of big indestructible stuff or combo pieces that opponents are using. Sidisi, Undead Vizier is good for tutoring for pieces that you need to respond to other people or just winning. It is also a good idea to run reanimate cards like Animate Dead, Necromancy Dance of the Dead, Victimize and if you have the money Sheoldred, Whispering One and Reanimate.

Thanks to both of you!

pjeseb-Grave hate isn't as big of a concern as in other metas, though there is a fair amount of it, so I might add a few cards. Yahenni is someone I will consider, though I don't know if they'll make the cut. This deck was helmed by Mazirek when C15 came out. Ultimately, I decided that while he was interesting, he didn't offer the best removal. And with him as the commander, I didn't have enough recursion to make him a viable option.

mazrimtaim-The dredge cards are kind of a hit or miss. To me it feels like I'm putting all my eggs in one basket, which makes it very susceptible to grave-hate, which, is as I mentioned, there, usually in the forms of Rest in Peace and Bojuka Bog. I don't really have any way short of Sun Titan to recur lands, so Gitrog is not something that I'm interested in. Even the extra card isn't usually going to be crucial, as I will usually just tutor up Skullclamp and/or Disciple of Bolas. Sidisi and Sheoldred are going in the deck once I get them. Duplicant is something I haven't considered, so I'll take a look at that. I know I should be running Animate Dead and friends, but I'm trying to use as few non-creatures as possible, because I was never able to do anything due to the low amounts of creatures. I will take a look at Animate Dead and Necromancy though, because those are really good. Turn 2-3 Razaketh, the Foulblooded seems fine.

So, I was wrong pjeseb. There is grave hate, however, things that grant me hexproof aren't useful, as the most common form of grave hate is from Rest in Peace and Leyline of the Void. Also, I misjudged Yahenni, and will give them a shot once I pick up a copy. I'm always looking for more sac outlets, so having one that also survives board wipes could be a massive help or just useful.

mazrimtaim- I did try some of the dredge cards, and ultimately decided that they weren't worth it, for the reasons I said above. I still don't think The Gitrog Monster is worth it though, because the deck doesn't revolve around it. People have been telling me that Victimize should stay in, though I'm on the edge. Usually it's just a dead card in hand, because if there is a point at which I can't really cast or recur things from my yard, it's either because it's been exiled or something is killing my creatures and I can't get one to stick for Victimize.