Jmdt was dead on that this deck is too slow to beat out a rush. But since this deck uses death, it can easily add one of the better rush stoppers out there, Bone wall. Bone wall blocks 7 attacks from enemy creatures, and even more if deaths occur on the field. With parasites, you're easily able to take down creatures using their ability. However, they are extremely fragile creatures. Nightfall doesn't give them the hp to survive much CC, but cloak is a great card to protect your easily vulnerable parasites. Another card that is interesting to add to this deck is the rare death weapon known as arsenic, which inflicts two damage and one poison counter to the opponent every turn.
Here is a possible deck you could use, that utilizes two arsenics:
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52q 52q 52r 52r 52r 52r 5un 5un 5un 5un 5un 5v0 5v0 5v0 5v0 5v0 5v2 5v2 5v2 606 606 606 606 606 606 606 606 606 606 606 8pk
Multiple bonewalls increases your chance to draw them, and the added ability to play one after it becomes broken is a great option.