You should have 4 entombs and 4 buried alives to increase your chances of drawing them since black does not have much drawing power.
Also, if you have 4 beats in play or 16 beats in play it does really matter. Having that many huge creautes is a "more win" type decision. Having less creatures also gives you room in your deck for more disruption, which gives you a better chance of getting a biggie into play. Pick only the best creatures to put in your deck. Maybe sideboard one or two depending on the metagame.
I personally play with more 10-12 reanimate type spells, the idea being: even if one of your beats is killed you can simple reanimate them again. Creatures are you livelyhood with this deck, there is no other way to kill your opponent. Make sure your have multipule ways of getting them out.
Finally, I have found Zombie infestation too slow for type 1. As for drawing a creature, if it is in first 7 mulli else you could you could always hymn yourself.

Though not an ideal choice, definitely possible. You may want to consider contamination against non-mono-black decks, and filth against black decks. Both cards have work well for me, though may not be 100% T1 cards. (Then again reanimator isn't really a tier 1 deck either.)
Hope this helps.
The Funk