Cards I don't understand: Myr Sire, Runeclaw Bear, Rot Wolf, and Natural Spring. None of them particularly fit with what this deck is trying to do - big and fast. Cards I don't particularly like: Scaled Wurm and Vastwood Gorger (too expensive). Cards I'd like to see more of: Pelakka Wurm, Whispersilk Cloak, and Cultivate. Cards I'd like to see: enchantments like Blanchwood Armor, ways to keep your creatures in play (like Regenerate) or get them back in play (Nature's Spiral), and more land grabbers, like Rampant Growth. I'm not too familiar with older cards, as I started playing around Zendikar, but there are probably some older cards that'll fit well. Also, in general, the deck looks a little too spread out. Try condensing the number of cards (i.e. 4 Apha Tyrranax instead of 2 Alpha, 1 Rot Wolf, and 1 Runclaw Bear). It helps give your deck consistance, and narrows your deck so it really focuses on doing at least one this well. However, I will always advocate the inclusion of removal spells. :)
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I really like the inclusion of Havengul Lich here - it allows you to sac cheap humans over and over to feed your demons I don't see why you couldn't include four of the Archdemons though - you'd have a better chance of drawing them, and it's not like you HAVE to transform them. I also really like what you're going for with the Wing Splicer - but I don't quite get the inclusion of the Mana Leaks and Negates. I feel like you'd be better served using that space for another gravepurge, Archdemon, or human. Neurok Invisimancer is always nice - not only is it a 2/1 unblockable, but it can make your Archdemon unblockable for a turn too! Village Cannibals gets +1/+1 counters whenever another human dies. Just some things to think about.
Another card to use is Spawnsire of Ulamog. He can get you more Eldrazi, and summon any other strong Eldrazi from outside the game too.
Not a bad deck. I'd suggest Smite though. or Reprisal.
Kabira Vindicator
Might I suggest the card Rith ,the Awakener? A 6/6 with flying, every every time you deal damage, you can potentially double the number of saprolings on the field.