doctorhydrogen

IMO you're lean on lands. 33 is tight for a mono deck, and seems really asking to get mana screwed in a two color. I'd up to at least 36, one of which could be a Myriad Landscape for some cheap ramp.

Speaking of cheap ramp things look lean there too, especially with a commander who is so expensive to cast. Dimir Signet, Talisman of Dominance, Commander's Sphere, Dimir Cluestone, and Dimir Keyrune are all fifteen cent cards, and will all help you get stuff into play faster.

If you don't mind spending a buck fifty or so, Dire Undercurrents tends to be a monster in Dimir.

Don't forget Greed as a budget card draw option. You've got Night's Whisper and Read the Bones, but I'd probably run Greed over Sign in Blood, unless you're just playing fast 1v1 games.

Remembrance is a bomb in Athreos apostles, as is Edgewalker.

You have two copies of Bladed Pinions.

Shizo, Death's Storehouse is a nice way to give Skullbriar evasion that doesn't really hurt your mana base. Yavimaya Hollow is really useful too.

Take a look at Essence Harvest. My friend who runs Skullbriar regularly kills people with it, swinging into one guy with a 20/20 Skullbrair or whatever and then Essence Harvest on a second for another 20. I can't imagine running it in may other decks but it does really good work in Skullbriar and in my +1/+1 counters Mimeoplasm deck.

Future Sight is a bomb in Talrand. I've chained half a dozen cards in a row of the top of the deck.

Guided Passage is tons of fun in Riku.

Future Sight has chained me half a dozen free cards in a row before with Talrand. It's cheap, too.

Both Dissipate and Dissolve are strictly better than Cancel, and both are like 30 cent cards.

Switcharoo makes you a token when you cast it, and lets you swap a token for their best dude, and it can't be undone by removing the aura like with Control Magic.

Executioner's Capsule is a Doom Blade that goes back to your hand after you use it with Glissa out so you can use it again.

Triangle of War is a Hunt the Weak that goes back to your hand after you use it with Glissa out so you can use it again.

Sylvok Replica is a Naturalize you can recurr.

Cultivate is a great card, but Expedition Map and Wayfarer's Bauble are also repeatable. I've put half a dozen lands into play with a Wayfarer's Bauble over the course of a game before.

Hall of Gemstone- It prevents counterspells (since you'll presumably be calling green) and it can dramatically shut down multi-colored decks.

Primal Order- Will straight up gut some multi-colored decks.

Not yet. I'm a weirdo about card prices; I don't mind spending cash or trading heavily for something I want if I think it's going to mostly keep it's value, but I'm a cheap-ass if I think the card may drop heavily. It's sitting at like 96 cards done because I don't want to buy or trade for Mana Reflection, Oracle of Mul Daya, Gauntlet of Power and Rings of Brighthearth because all could easily become 5-ish dollar cards if they show up in MM15 next month.

I spent most of EDH night this week determining that my creaturelss Sydri deck isn't gonna work, and finding out that my Talrand deck is infinitely more fun the more counterspells I remove.

You have Hooded Hydra and Inspiring Call entered twice.

With that many creatures Lurking Predators would be huge. Like back-breaking.

Harmonize is a great card, don't get me wrong, but in a deck like this where I think you're gonna have a lot of huge bodies on the field I'd take a long look at Soul's Majesty. I replaced Harmonize with it in my +1/+1 counters deck, and I don't think it's every drawn me under 5 cards, and there's been times I've drawn 15+ off it.

Corpsejack Menace is so good in a counters deck it would be worth running some swamps for it, imo.

I might run Primal Surge over Genesis Wave, just because it's hilarious when you're able to chain 40 cards in a row. Still, on average GV is probably more consistent.

In a deck with this many creature spells Lurking Predators would be nuts.

Don't be afraid to just show up at your local game store, either. I spent about six months with only one friend to play with, and for the hell of it we just started showing up at our game store on Tuesdays to play each other instead of my house. After a month of just the two of us another guy started coming weekly, then another, and now 18 months later Tuesday night EDH is something the store promotes and we've got probably 15 regular players. All because we just walked in, sat down, and started playing at the same time every week.

Future Sight. I've played like half a dozen cards in a row off it before.

Dismiss into Dream? Make them sacc the stuff you tap. Plus it makes it so they can't equip anything, use auras, targeted buffs or abilities, etc.

There' s almost no downside to Villiage aside from it coming into play tapped. It hurts tempo slighty for one turn, and after that it's a mountain. That's very little downside, but in a long game being able to immedietly swing with a 14/3 Spellheart Chimera or attack with your Titan to lock down another target it can be invaluable. It's low downside with solid upside. Next time you're in a game just ask yourself how often haste would be useful with this deck. I bet it's more often than you think, especially when it costs so little to add it to the deck.

As for Recurring Insight, unless you're playing with really bad people it should always get you a ton of cards. If you're playing with opponents who are in top-deck mode then yeah, it's crappy, but if you're playing EDH with people in top-deck mode you should be able to win with a pre-con anyway. And while I get what you're saying that 1-2 mana is a lot, it's so much radically better than Thoughflare in almost every situation that the one mana is worth it. Same as with Villiage next time you're playing and have Thoughtflare in hand look at the table and think "would I be better off with this, or Recurring Insight?" If you answer Thoughtflare even one out of ten times I'd be shocked.

All that said, each meta is different, and what makes for a good card in mine doesn't necessarily translate into yours. There may well be a ton of variables regarding decks, playstyles and personalities that I don't know about, so in the end you're the best judge of what plays best.

Good luck with it!

Maelstrom Pulse would work here

IMO you're running too many lands, especially in a deck with no good way to get them into your hand to play them.

Me personally I'd drop down to 40 lands and fill those 13 slots with land ramp (Nature's Lore, Explosive Vegetation, Skyshroud Claim, Cultivate, Kodama's Reach, Rampant Growth) and draw (Sylvan Library, Greater Good, Hunter's Insight, Harmonize).

Overwhelming Stampede basically lets you kill anybody when Omnath is over 10.

Couple more things in thinking on it:

Protean Hulk is banned in EDH.

Birthing Pod could be great here. How many times are you sitting at 20 mana in Omanth but you can get past chump blockers, etc. Podding a Garruk's Horde into a Craterhoof would win the game. Omanth is also a great pod target. Pod Omnath into Nylea or Karametra's Acoylyte, then recasting Omnath immediately could turn the tide. Speaking of Nylea, she should have a slot :)

Same for Greater Good. Even if you just use it to sacc a dude that's dying to a board wipe or targeted removal anyway it's a good card, but being able to go over the top in a stalemate by saccing Omnath, drawing 15 cars, and replaying him immediately seems like the kind of thing that could flat out win a game.