If you are having trouble against Control and Grixis Shadow, you should probably run more Voice of Resurgence. It's the best card to use for Eldritch Evolution anyway, and really makes life difficult for decks that use countermagic, spot removal or attacks on the ground.
I personally run 4 Voices in my Saheeli list and would play 6 or 7 if I was allowed to do that. There are some matchups where it's basically a Grizzly Bear, like Storm or Affinity, but in many other matchups drawing multiple Voices gives you a very high chance of winning. At the very least, most opponents will need to deal with the Voice(s), thus creating opportunities for your other, slower cards. If they have to Path to Exile it on turn 2 or 3 (on their own turn too), you get to untap with a lot of mana.
Another great tool to beat grindy decks is Tireless Tracker. I only run one, but it's a fantastic stand-alone threat that can generate serious card advantage and pressure without overextending into a Supreme Verdict, All Is Dust or the like.

Emzed I have seen that other lists run more Voices, but for now i really don't see reason for it. Tireless Tracker should be on "Honorable Mentions" i just forget to add him.

In your own deck description you mentioned some bad matchups, and Voice is very good against serveral of those. So there is your reason to play the full 4 :D
Honestly, Wall of Omens is okay, but Voice is so much better in my experience. A 0/4 blocker is just rarely relevant in a metagame dominated by Storm, Eldrazi, UW Control, Death's Shadow, Company and Affinity. Voice is actively good against some of those decks, and attacks for at least 2 damage against the others, more if you can get it to die.

Just a point I think you missed in the description, if you have one saheeli out and one in the graveyard (or two in the GY), you can go infinite by tutoring up sun titan, getting back saheeli, duplicating sun titan, and getting back a new saheeli. The only issue with this is that you seem a bit short on 4 cmc creatures that can find sun titan.

jld592 I have not think about that, but yes it does go infinite.

i think you should try using a 2 mana creature like Sylvan Caryatid harder for opponent to get rid of and can produce mana for evolution to get felidar guardian, he is also a good blocker in aggro matches.

frogkill45 2 cost mana dork? No thanks. If i want more mana dorks i would play Noble Hierarchs.

You know 2 mana dude that just produces mana is not even close enough good for this deck, it is so terribly slow. Yes Hexproof is very good but still, it's power level isn't enough for Modern (Usually). Mostly Wall of Omens takes this slot as better blocker and overall drawing card is just better.

If you think about decks other 2 drops:

Lotus Cobra Can produce huge amount of mana with fetchlands.

Voice of Resurgence Maybe best value creature in whole Modern format.

Scavenging Ooze Our main deck hope against Storm and Dredge, bit situational but still very important.

Wall of Omens Doesn't seem like amazing, but blocks much better and draws card which is so good.

Thanks for you suggestion, but there is reason that 2 cost mana dorks are not played in Modern too much.

Sylvan Caryatid becomes a little more interesting if you run Worship since it rarely dies in the matchups where you want Worship and it accelerates you nicely into the 4 mana enchantment. But that's about the only real reason pro Caryatid, it's just not what this deck needs, since you want to ramp into 3-drops.

Emzed That is then whole different thing. Worship is of course option but i don't just think it fits in here. Deck would have to be changed a lot.

In my experience Worship is a great sideboard card against decks like Burn, Merfolk, Dredge, Living End, Death and Taxes, some versions of Elves and other Aggro or Combo decks. I like it against Affinity too, even if they still have Inkmoth Nexus to get around it. You can adapt your deck a little to accomodate Worship, such as Courser of Kruphix to keep fetchlands online once you're at 1 life (your list even has two Coursers already), but it's not really necessary. Worship is good enough on its own in a deck with this many creatures against most linear, damage based decks. They can rarely beat it, and neither can they prevent you from eventually winning via combo.