I'm elated to report that I managed to make it to the Top 4 at Grand Prix Minneapolis this weekend, a result made only sweeter by the called-shot nature of giving a rundown of the deck I piloted last week. I did make a couple of last-minute substitutions, so let's start there.
I was playing sixteen Mountains as the manabase for early builds of the deck, and recently I landed on going up to eighteen total lands by adding two Horizon lands. They provide marginal equity in grindy matchups, and playing them in spell slots allows them to be discarded to Faithless Looting when your life total is to be used as more of a resource. I'm pretty happy with eighteen lands at this time in most matchups, but more on that later.
The major update I made for last weekend was to eschew both cards that I had been waffling on for my last two spell slots for a different card entirely. Going into the weekend, I was weighing whether the spots where Gut Shot or Blistercoil Weird were bad were more common, and ultimately I decided to play neither.
To elaborate, Blistercoil Weird is fundamentally weaker than the other one-mana creatures in the deck when it comes to Wrenn and Six, responding to Collective Brutality with instants, and just combat in general. Gut Shot is weak outside of specific hands or situations where it's a zero-mana Doom Blade, and in many ways is too heavy on such a marginal effect to have in the deck next to four copies of the superior version of the effect in Lava Dart, which plays better both by working as two spells and by being a good discard to Faithless Looting.
The card that I ended up playing in this slot, Burst Lightning, seldom gets a lot of love in Modern. In the context of the current format, though, a one-mana instant that deals two damage is great against much of the common opposition in the format like Hedron Crab, Eidolon of the Great Revel, and Meddling Mage.