So far, so good. I've run multiple iterations of this deck, and this is the one I prefer thus far in Bo1 (around 65% win-rate). The goal of this deck is to survive until alpha strike (Harbin, Vanguard Aviator). Because he's our main win condition, we play with the full playset : the first one may get played on turn 2 and die to removal, but we'll use Recruitment or Skystrike Officer to dig for another copy.

Survivor of Korlis is better at buying time than Yotian Frontliner or Spectrum Sentinel, thanks to first strike (on steroids with Valiant or Siege Veteran). Multiples stack on defense, and Scry 2 for 1W after it chumps is great later in the game. Also, it can get replaced by a token with no loss of power on the battlefield, thanks to Siege Veteran.

Resolute Reinforcements has a lot of synergies : with Siege Veteran, the non-token 1/1 can block (or sac to Liliana), and you'll lose no power on the battlefield ; with Skystrike Officer, you can draw an extra card right away on turn 3 if played previous turn ; with Valiant Veteran, to compound on the anthem ; with Harbin, Vanguard Aviator, to populate the army he needs to trigger his ability ; and finally with Myrel, Shield of Argive, to create even more tokens.

Also, passing our turn 2 while opponent kept mana open may mean they've lost a full turn hoping to remove a threat that will only materialize at the end of their own turn. Players that lose a turn that way are more likely to tap out on their next turn, which greatly increases the chances to play a Siege Veteran or Skystrike Officer and get some benefit from it before it gets removed. Because it makes all other cards so much better, I consider Resolute Reinforcements core to this deck.

I want no less than 4 Myrel, Shield of Argive in my deck. Because of her, Valiant Veteran can't get removed to screw my combat math ; The Wandering Emperor can't ambush us ; removals can't deal with Harbin on alpha strike ; Bankbuster can't be crewed or activated ; Blood tokens can't be sacrificed ; etc. More importantly, she's our removal magnet. She can't be ignored, and will thus die to the next removal instead of Skystrike Officer, Brutal Cathar, Valiant Veteran or Siege Veteran. That's a great quality that neither Guardians have (Thalia, Guardian of Thraben and Guardian of New Benalia).

Myrel is obviously one of the reason the Guardians (Thalia/Benalia) got cut from my deck. But, really, I just don't think these cards are better than the ones I've assembled TOGETHER. The lists that play these either play with less than 8 one-drops (not enough to feed Skystrike Officer or Harbin), less than 4 Harbin, Vanguard Aviator (our win condition), less than 4 Resolute Reinforcements (huge synergy with the whole deck), less than 4 Skystrike Officer or 4 Siege Veteran (wtf), and some quantity of Dennick, Pious Apprentice (which I tested and really liked, but choices were made). Some lists also play some non-creature spells (In the Trenches, Protect Negotiators, Soul Partition, etc.), but I find these hinder our main plan, while chump blocking once or twice (and sometimes not at all) is often enough to reach alpha strike. 20 life is a nice ressource to give us time, and it's only in the control matchup (with Farewell), that this plays against us (but we can't win them all).

23 lands could be enough for our curve, but not missing our third land drop is very important. Also, while flooding is never fun, games are won activating Fortified Beachhead (needs 6 lands), or using Recruitment Officer to fetch and immediately play one of our lords (Harbin/Valiant) (also done with 6 lands). Using a dead Valiant Veteran with 5 mana to add counters to our army for the win is also an interesting play. For all these reasons, 24 lands is what feels nice for our build.

Finally, the mana base is perfect for our curve : 15 sources of untapped U to cast Harbin on turn 2 (excluding Deserted Beach, including Plaza of Heroes), or Skystrike Officer on turn 3 (excluding Plaza, including Beach) and 21 sources of reliable W (considering Plaza), including 19 to play untapped on turns 1 and 2.

I tested Mishra's Foundry, but much prefer the option to protect Harbin or Myrel with Plaza of Heroes.