I'd take out 2x Hinterland Harbor for 2x Eldrazi Temple.

Jin-Gitaxias, Core Augur, Lorthos, the Tidemaker could be side boarded and in their place 1x Kozilek, Butcher of Truth and either 1x It That Betrays or 1x Artisan of Kozilek.

Lotus Cobra would be HUGE here! Especially if you added in a few sac/fetch lands like Misty Rainforest, Scalding Tarn, or Verdant Catacombs.

Eternal Dominion would also be better suited in the sideboard. In it's place you could run 2x All Is Dust. Best removal in an Eldrazi deck period.

I'm torn over Garruk, Primal Hunter. He seems cool, but I think you'd benefit more from Garruk Wildspeaker. He comes out earlier, gives you ramp, tokens, and his ultimate is Overrun.

I like where you're going with this. I have a similar deck, but Legacy:

Touchdown! Da LOL's

I tested this against my deck:please-beat-this-deck. It did very well! Both decks are super fast. I retract my statement about Garruk, Primal Hunter. He's a beast...

I like this deck. Only criticism is that you don't have any mid range creatures or life gain to keep you alive. Maybe take out Eternal Dominion. Its a cool card but this deck is more about the Eldrazi. I would also recommend taking out Mind Spring. Maybe not all of them but 1 or 2 so you can put in some life gain or creatures to block. This deck seems like it works but not consistently. That and its horribly expensive. I have an Eldrazi deck Spawn of the Eldrazi thats under 100$ and is super fast. Take a look at it sometime.

Ok, so I removed 2 Mind Spring and 2 Hinterland Harbor, as well as the 2 Eternal Dominion.

Added in 4 Kozilek's Predators to give me some mid range creatures, and added in Kozilek, Butcher of TruthAlso 2 Eldrazi Temple

I see way too mana ramp, -2 Birds of Paradise. Those thallid don't have anything to do in there. remove them all and put 2 Chancellor of the Tangle and 2 Vorapede for instance.

Terra Stomper Is always nice in mono green. 8/8 Trample, and cant be countered for 6. Cant beat that.

Lotus Cobra is more or less required with Primeval Titan, and you did that, then Harrow would be better than Rampant Growth

Overwhelming Stampede > Overrun.

And you might as well put a red sources or two and 2x Kessig Wolf Run in here. You don't really have a reason not to.