democidist

Afterlife Insurance is missing from the decklist proxied by Brave the Elements.

This is a net deck based on:
https://mtgtop8.com/compare?l=_447196_446969_440074_
I adapted it based on old Standard Simic Tempo decks and some Pioneer Simic Tempo lists.

I was also surprised that there were no can trips in the lists, because I feel like they'd increase consistency. Sinister Sabotage is sadly one of the best counter spells in Pioneer. There is no goal to dump things into the graveyard, there's no delve or other graveyard-matters cards. Magma Opus dumps itself and isn't the only card that you can flashback with Torrential Gearhulk.

Without fetch lands for mana fixing in Pioneer, the mana based gets bloated with additional colors, which is why most of the top decks in the format are only two colors. The triomes enable nearly the entire deck to come in untapped, their purpose is not to cycle for highly inefficient card draw.

I'm not convinced that mainboarding Extirpate is a good idea. Personally I'd try to make room for some Thoughtseize, Kaya's Guile, and maybe Fatal Push mainboard. If you choose to move towards a more Baneslayer-esqe style, even just as a post-sideboard plan Spirit Bonds is nice, especially paired with Not Forgotten. I'd probably cut Elspeth, Knight-Errant and Sorin, Lord of Innistrad in favor of Gideon of the Trials. You'll be working off of a VERY slow clock with only a few tiny tokens, consider adding Intangible Virtue. If you choose to go that route: Secure the Wastes, Sram's Expertise, and Spectral Procession are all good options. In Orzhov colors you'll be able to more quickly rebuild after a boardwipe than most decks.

I understand that it's always a careful balancing act of creatures to other spells in decks like these, but I think that especially in commander you'll need a few more than 13 creatures. You won't want to have to rely on recasting your commander that heavily.

Maybe sideboard Leyline of Sanctity for burn?

Is this a standard deck from when RTR was still in standard? This isn't a death and taxes deck, you don't tax them at all; Death & Taxes uses cards like Thalia, Leonin Arbiter, or Ghostly Prison to make it much harder for an opponent to enact their game plan.

That's an aweful lot of tapped lands you have there. You're basically going to be playing the whole game a turn behind because of it.

That's definitely something to consider as a sideboard option. I'll have to keep it in mind.

Death's Shadow will raise the cost of this deck significantly, especially after accounting for its support cards. Depending on your definition of budget, which given the current estimated value for this deck is likely pretty strict, you may want to reconsider running it at all.

Since both are unconditional it's not terrible value, but it's not amazing. There comes a time in every match where mana isn't the restriction, and you just need to be able to … do things, and that is where cards like Far // Away accel.

I wasn't complaining about the card advantage/disadvantage situation, I'm talking about how you're still three-for-one'ing yourself and how Thought Scour is just taking up slots in your deck that you could be using for something that contributes in more ways than just fueling delve which nearly every card does naturally. I suggested Far // Away not because it's the best card ever, but because it helps your deck specifically. Modern is a value format, if your deck can only one-for-one or worse, it'll be rough and the value Far // Away can generate is solid because you can just cast half, or you can cast both if you wish.

Two Thought Scour in your opening hand enables a turn two Angler, but that means that you'll have effectively spent three mana and three cards to get a 5/5 onto the battlefield which is really quite bad value, even if it is fast. They will likely just remove it before the turn three that it can finally swing on. By contrast, Duress breaks even by way of making them discard and Opt at least gives you a bit of draw control. Relying on the deck's namesake isn't such a bad thing, but protecting your creatures when you have so few is a good idea. Far // Away over Vapor Snag would help with all of this, btw.

You need more removal and/or counter spells if you want to have such a small creature base.
I'm not sure why Thought Scour is in the deck at all as it doesn't do anything your deck cares about. Can-tripping is fine, fueling delve is fine, but you can do that with actual value using something like Doom Blade or Despise.

Have you considered Secure the Wastes, or splashing black (via Godless Shrine) for lingering souls?

Playing cards like Elvish Mystic and Rattleclaw Mystic would make your Jeskai Ascendancy win condition more consistent than relying on Awaken to get the six land creatures you need to go infinite. Also, I suspect that Defiant Strike would be particularly strong in this shell. I would also like to see the cards that are core to the strategy become 4-of's particularly Jeskai Ascendancy since the deck doesn't work without it.

You should consider Elixir of Immortality for more consistent creature recovery from your graveyard.

You need more ways to make sure that Laboratory Maniac hits the battlefield first. Also, it still looks like you don't have enough cards that grant you mana.

Basilisk Collar anybody? Or maybe Quietus Spike?

You might be missing some lands there...

Looking at your deck just reminded me of mine, because they both involve card advantage and draw control. I just thought that you may be able to apply some of the ideas from my deck to yours. Also, I wanted to recommend that you squeeze in Despise. I'd swap out some removal for it and call it good.

AZ88: I wasn't trying to suggest that you need less lands.
KJSJ3: I realize that the deck isn't in standard anymore, but many of the ideas from it are still around and playable. Thanks for the link.

Apparently the link broke, so here's a new one: http://www.mtgvault.com/democidist/decks/standard-dimir-midrange/