I play red eldrazi myself, and I feel like the best are ones that keep the same shell as serum powder eldrazi stompy with red for obligators/hazorets/chandras in the main and other red cards in the side.
Before WAR I was feeling that red Eldrazi was the better choice, but the addition of blast zone makes me question that a bit. There just isn't space for it in red Eldrazi, and the advantages of red just don't feel as worth it now.
Do you side in the hate rocks in G2/3, or not? If so, do you side out Karn? How do you accommodate the fact that he only tutors from exile?
I've been testing Karn and I really don't know how to side yet. If I side out Karn, the hate rocks obviously go in, but in other cases, I side in all but one of a hate rock, so Karn can get one from the side and isn't completely dead. My 1x hate rocks don't ever really get sided in if Karn stays in.
Have you tried some number of Bound // Determined in this build? I'm trying various Dinosaur Wrangler builds right now (my preferred name for this deck), and I find that they can be a bit slow at finding the combo sometimes. Bound // Determined is a cantrip (so it can help you dig for the combo), it's 7 cmc and green (so it pitches to Nourishing Shoal well), it's also black (so it pitches to Soul Spike well), and it even staves off counterspells. I'm concerned that 4 Iname as One don't dig for the combo well enough.
I think I'd rather just run something like spell pierce or something to protect the combo. Hitting 4 mana is rough, and there's still plenty of cards that pitch to shoal, spike, and allosaurus rider.
I haven't really liked Scavenger Grounds in this deck, so I think I'll cut both and my third Gemstone Caverns for 3 Explosion Zones. Having a mainboard boardwipe and out to bridge is super powerful, but it's important to note that Explosion Zone doesn't kill tokens.
Here's my list:
1 Endless One
4 Eldrazi Mimic
4 Eldrazi Obligator
4 Eternal Scourge
4 Thought-Knot Seer
4 Reality Smasher
4 Simian Spirit Guide
Instants
4 Dismember
Artifacts
4 Chalice of the Void
4 Serum Powder
2 Blast Zone
4 Eldrazi Temple
2 Gemstone Caverns
2 Ghost Quarter
3 Mountain
4 Ramunap Ruins
3 Sulfurous Springs
2 Mutavault
1 Fiery Islet
2 Abrade
3 Relic of Progenitus
1 Sudden Shock
2 Alpine Moon
2 Rending Volley
1 Hazoret the Fervent
4 Leyline of the Void
4 Eldrazi Mimic
4 Eldrazi Obligator
4 Eternal Scourge
4 Reality Smasher
4 Simian Spirit Guide
4 Thought-Knot Seer
4 Dismember
4 Chalice of the Void
4 Serum Powder
1 Surgical Extraction
2 Blast Zone
4 Eldrazi Temple
2 Gemstone Caverns
3 Ghost Quarter
3 Mountain
4 Ramunap Ruins
2 Sulfurous Springs
2 Mutavault
1 Fiery Islet
2 Abrade
2 Anger of the Gods
1 By Force
3 Alpine Moon
2 Rending Volley
1 Hazoret the Fervent
4 Leyline of the Void
I've been testing Karn and I really don't know how to side yet. If I side out Karn, the hate rocks obviously go in, but in other cases, I side in all but one of a hate rock, so Karn can get one from the side and isn't completely dead. My 1x hate rocks don't ever really get sided in if Karn stays in.
I think I'd rather just run something like spell pierce or something to protect the combo. Hitting 4 mana is rough, and there's still plenty of cards that pitch to shoal, spike, and allosaurus rider.
1 Forest
4 Forbidden Orchard
4 Gemstone Mine
4 City of Brass
4 Mana Confluence
2 Griselbrand
4 Nourishing Shoal
3 Assassin's Trophy
4 Soul Spike
4 Iname as One
4 Serum Visions
4 Allosaurus Rider
4 Summoner's Pact
4 Eldritch Evolution
4 Neoform
4 Simian Spirit Guide
1 Seismic Assault
3 Gigadrowse
2 Fatal Push
1 Void Snare
2 Echoing Truth
3 Spell Pierce
4 Chalice of the Void