So the reason I made this deck is twofold:
Butcher of the Horde is a crazy good creature that needs feeding, (read Tokens), and in the same colors there is Rabblemaster, Brimaz and Monastery Mentor.
Secondly there is Crackling Doom that is both critter removal AND a damage dealer. Cant beat that...
The deck started as a more Warrior Aggro build and has over the past few months evolved into what you see here, (see below for playtested cards).
Took the best critters I could find for a Mardu Tempo shell and made sure they all feed off each other like Butcher + Rabblemaster and Brimaz. Seeker + removal and Sorin/Sarkhan plus the newest arrival, Monastery Mentor, that slips into both slots.
The base idea behind this deck is to gain value in increments over your opponent by playing critters that give/leave something extra and slowly take over the game in that manner.
The deck sits right on the border of an aggroish deck that can hit pretty hard early and a more grindy mid-range control build that wins by tiny tempo gains each turn. Fun to play because of the interactions and unless completely mana hosed you are rarely outclassed in any matchup.
The land mix pretty much sorted itself out with very little fiddling around but is working great, even though it does bring quite a bit of pain so the lifelink comes in handy.
Cards on the backburner that were not tested were:
Deflecting Palm looks fun but I wanted to stay away from reactive cards as they fit a more midrange/control shell.
Hordeling Outburst is played in every other build and I acknowledge that it is a good card but I'm just not entirely sold on it, but if it was an Instant it would be an auto include.
Magma Spray has always been a SB staple for me but lately my local meta does not have a lot of reanimation besides Whip so it has been left on the sidelines for now.
Dictate of Heliod could certainly slip in here as the only Anthem but at double White and five total to cast it seems like a stretch. It feels like a win more card. I could be wrong here...
Ankle Shanker is also, (sadly), too damn expensive to cast.
Elspeth is a potential game winner but would likely sit in the SB for game one...
Jeering Instigator as a pure Sideboard option looks great against Green Monsters but useless everywhere else.
Turn one plays you are looking for a tap land to stage your T-2 & T-3. Turn two Seeker or removal at the ready. Turn three Rabblemaster or Mentor, (remember this when you evaluate your lands in your starting hand). After that the possibilities are endless but a Butcher is never a bad thing...
Early pressure is often key but if you can draw removal on your Seekers and respond in return then your three drops end up being even stronger, (playing a Rabblemaster on turn three AFTER swinging with a Seeker to draw a removal spell is a perfectly legit play). Remove anything dangerous that is in your way and turn things sideways to win.... (well, it is slightly more advanced then that but I'm sure you'll figure that part out as you read on).
Again: Curving into the Rabblemaster - Butcher setup after dropping a threat or removing any opposing threats is your main objective. Brimaz is another one that tested well within these parameters but double white makes him often a Rabblemaster #5 that arrives a little later.
Flamewake Phoenix was one of the latest addition to the test cycle and the way it interacted with Butcher exceeded the most optimistic predictions on my part! Bouncing it back without Butcher on the field is also relatively easy as Sorin will pump up enough of the other critters to activate a Ferocious trigger. The double red is a major drawback in a deck that leans so heavily on White as this does though.
Valorous Stance looks like the difference maker that will give Mardu an edge in the arms race we see in the current Standard meta. Being able to gain ANY tempo advantage with the creatures available to the Mardu player might be all it takes to grab the top spot, plus it totally hoses control when they have to use two removal cards to knock off one of your critters.
Don't be scared to tap out in the early rounds to drop threats as this deck carries more of those then the average midrange deck, but ease up after round four or so, especially if you are holding a Crackling Doom.
Tokens are expendable, being sent on suicide missions to trigger stuff, gain you some life under Sorin's +1 or boost Rabblemasters is what they are here for.
More then 3 months of playtesting results:
Foundry Street Denizen had a long run in this deck as it interacts well with Rabblemaster but he got pushed out when I realized that the need for additional removal exceeds the early damage it delivers.
Soldier of the Pantheon works fine as a White one drop and it's protection looks awesome but it felt a little blah when played compared to the other little guys as it has little to no interaction with the rest of the deck. Dropped it to playtest with Akroan Hoplite, a card that looks fantastic for the two drop spot. Turns out I feel the same way about the Hoplite as the Soldier, (unless you choose to play Iroas in the main)...
Enter Chief of the Edge and Bloodsoaked Champion that also had long runs when the deck was Warrior focused, she pumps the other little guys up to where they will take out a Caryatid and should two of them come along then nothing was safe. Champion just keeps coming back from the dead causing all kinds of havoc. Tymaret, the Murder King also stuck around for a while until I had to make room for that additional removal, (directed mostly at the currently hot Abzan decks).
I finally have seen the light and included Seeker of the Way! It took some tweeking of the removal suite for me to make the switch from the Chief and Co but now I have enough triggers for it to be worth using his Prowess.
Crackling Doom easily turned out to be better critter removal then Hero's Downfall in here, (and the extra damage is a BIG deal), so I went all out on those and cut tje number of Downfall's, (something made relatively easy as Utter End is mainboarded), A different Edict effect I had some good experiences with coming out of the SB was Dictate of Erebos. Looks a little slow but actually ends the curve nicely against the decks it targets and the Flash can be brutal, (trading Goblin Tokens for big Green things is always fun), but it got phased out for Hushwing because of the need to hit opposing Siege Rhinos and its additional evasion.
Wingmate Roc was late to the test cycle as I thought it to hard to cast and to late in the curve to be a swing card. However, after the need for additional lifegain against midrange decks became obvious it quickly showed me what a powerhouse it is, (triggering Raid is never a problem and being at the end of the curve ensures double White available). One is good, two of them is plenty.
However:
I finally got my hands on some Monastery Mentors that sidelined some of the Roc as the Mentor went straight into the deck, and they are just as advertised, a damned beast that can take over the game for 3 mana! If you have them, play them!!
Mardu Charm was a bit of a letdown because it looks like it has everything this deck needs but then the testing showed it as somewhat underwhelming, (as there is no damage to the head and the other effects are simply overpriced Raise the Alarm and Duress), and it can be booted from these builds entirely except that in this deck it interacts well with Mentor, (and in earlier builds Puphoros and the Chief), and it takes out a Courser, (or snipe what scary spell they just drew in their draw step), or an opposing Butcher so they kind of hung around until I found something superior. Stoke the Flames is clearly a better play if additional damage is what you are going for.
Ride Down surprised me in a positive way after extensive playtesting with Denizen in the main. Not only does it flat out work wonders with Rabblemaster, it also messes with your opponents blocking plans after you flashed the first one, BUT if you are not running Denizen and/or Hoplite in the main it is to narrow with only Rabblemaster as the prime beneficiary. The new critter enhancer Temur Battle Rage might work even better as it has fewer strings attached...
Note that they will also often be boarded out when your opponent loads up on critter removal from their sideboard.
Mardu Ascendancy can get nuts with Rabblemaster in play but can sit around in your hand when the board is critter free. This is a tricky one to find the right number of, three seems fine but four is certainly playable in this build. Should you decide to go with four then two or three Purphoros is definitely an option. Currently not in this build because of the need for additional removal but could quickly rotate back in if/when the meta changes.
Tested with singletons of Hammer of Purphoros, Iroas, God of Victory and Athreos, God of Passage, all worked very well. However, later testing with multiple Iroas, God of Victory did really shine when Rabblemaster and Ascendancy start doing their thing. I won't discard the possibility that there is an even better combination of those that I have not noticed available. Whip of Erebos is a different life gainer with the occasional Ball Lightning effect built in and plays very strong out of the SB when your opponent loads up on destructive removal.
The Mana base was surprisingly stable from the getgo and the one major thing I ended up adding was the Bloodstained Mire. Mana Confluence can be played instead of the taplands if you are not playing Sign in Blood or Read the Bones.
Other playtested cards were fine but did not break any records and can either live in the Sideboard or enter when meta dictates. One exception is Bile Blight, it still rocks as a removal card that slays Tokens and don't forget that it also gives you some very good combat tricks. If you are not playing them mainboard then keep them handy in the sideboard!
Sideboard includes removal that exiles rather then destroys, sweepers to clear the board of pesky little things as well as big stomping things coming for you. Hushwing those Siege Rhinos and snakes and swing over them, the God gives you the edge in the games where lifelink is a factor.