This is the mirror, so the game is decided by who develops the biggest threats fastest and who can punch through blockers. Surrak, Elusive Hunter is uncounterable trample that races well and dodges nothing the mirror typically has. Hard-Hitting Question lets your creature fight down their Mossborn Hydra or Mightform Harmonizer before they can grow further, which is huge against landfall-doubled counters. Shared Roots is a pure ramp card that doesn't impact the board and is replaceable with equally or more impactful threats and interaction in a mirror where tempo matters. Keep your mainboard curve otherwise intact since landfall synergies are symmetrical and this is mostly a resource race.

Dimir Midrange gets a lot of value from Enduring Curiosity coming back from the graveyard after it dies. Soul-Guide Lantern answers that: it can be activated at instant speed, so cast it early and keep it ready. When Enduring Curiosity dies, sacrifice the Lantern in response to the return trigger to exile their graveyard, and it won't come back. The Lantern also draws a card later if the graveyard plan isn't needed. Torpor Orb shuts off the enters-the-battlefield triggers on Floodpits Drowner (tap and stun), Dream Beavers (drain and scry), Spyglass Siren (Map token), The Wondrous Wasp, and Tishana's Tidebinder, which is a big tempo and value loss for them. It does not stop Enduring Curiosity's dies trigger, so don't count on it for that. Shared Roots and Sapling Nursery are the weakest cards here. Shared Roots is a slow, low-impact play, and Sapling Nursery costs eight mana minus one for each Forest, so it is expensive early against a deck with efficient removal and counterspells. Both come out for proactive disruption. Keep your core landfall threats, since this matchup is a race to go over the top before their removal (Bitter Triumph, Requiting Hex) and counterspells catch up.

BRG brings in Strategic Betrayal and other removal/disruption, so an uncounterable threat like Surrak, Elusive Hunter is excellent at dodging their answers while providing a card-draw bonus whenever they try to interact with your other creatures. Warg Tactics gives a key threat hexproof and trample to push through removal like Maelstrom Pulse or Requiting Hex and close out races against their Smaug or Wolverine. Shared Roots is too slow against a deck with efficient removal and proactive threats of its own. One copy of Keen-Eyed Curator comes out since it's a mediocre blocker against their bigger bodies and the graveyard hate isn't a priority here; the remaining two copies stay for incidental value.