State of Standard
Standard currently is experiencing one of the healthiest and brightest moments of the latest years as well as being definitely (and by detachment) the most intriguing and diversified format available on MTG Arena at the moment.
The diversity of decks we are seeing in recent months (and more markedly from the release of Duskmourn onwards) is making the format appealing and very balanced.
Many strategies are currently available and perhaps the only kind of deck that is relatively absent is control.
Among the various decks currently played there are not only Dimir Midrange but also Golgari Midrange, Golgari Ramp, Gruul Aggro, Monored Aggro, Azorius Tempo, Jeskai Convoke, Boros Aggro, Boros Convoke, Rakdos Aggro, Mono White Control, Dimir Control, Simic Otters and Domain Control/Enchantments. A list of playable and valid archetypes, in short, very dense and to which we have hardly been accustomed in Standard.
Unlike in the past, it is difficult to define a deck that totally dominates the rest of the metagame. If we think about last year, we remember how Esper Raffine was the undisputed king of the format. If we move another year back (before the ban of Fable of the Mirror Breaker to be precise) we had first Grixis and then Rakdos Midrange. Historically the pool of viable decks in the format has always been very small. Now, however, probably also thanks to the extended length of the format, we have many alternatives all valid in their own way.
Despite these necessary premises, I think that Dimir Midrange is slightly ahead of the other decks listed and, personally, if I had to play a very important tournament in the short term, I would probably choose to play Dimir Midrange.
If you want to play another type of Midrange deck, surely the choice would fall on Golgari Midrange but it has a very unfavorable matchup against Dimir Midrange. Also, from the many data available online, Dimir Midrange is the most popular deck at the moment. This is another disadvantage for Golgari Midrange.
It must be admitted that, at least during the games preceding the sideboard, Dimir Midrange is not an excellent option to counter aggressive strategies like those of Mono Red Aggro, Gruul Aggro or Boros Aggro.
Considering that the above-mentioned archetypes cover just under 30% of the metagame (when taken together), it is easy to conclude that the deck inevitably has weaknesses. Clearly, suffering 30% of the metagame is something that cannot be underestimated. The sideboard can definitely help a lot and if you want to tackle those matchups with more peace of mind, there are some adjustments to the main deck certainly possible. The risk is, however, to lose too much hedge against the rest of the decks which (if we exclude the mirrors) count for a little more than 50% of the total games.
It is therefore perhaps desirable to accept the fact that some aggro lists are tough to beat for this archetype and at the same time work on both sideboard and main deck to make sure that in 70% of cases the deck can give its maximum pre-sideboard and that in the remaining 30% of cases the deck is still able to face the matchup with a decent victory margin.
The list I’m proposing today is in fact only one of the many that can be found online and it is not the list itself to be analyzed today as much as the archetype. We could certainly discuss the exact number of copies of each card to be played but the conversation would, in my view, be meaningless and very sterile. In fact, considering that the gameplan of the various lists is identical, what matters is how they are able to deal with the various matchups. Having more removal benefits us in some matchups and disadvantages us in others, as well as having few counterspells puts us very much under pressure in some cases and makes us happy in others. The point is not to get to the exact number of copies per card to play as much as to understand how and why this archetype works so well despite the presence of some bad matchups.
Why do I think the deck is the best in the format?
First of all, we have a good clue: historically, in Standard, the most played deck is also the strongest. In this case, Dimir Midrange is played by about 20% of players in the format. Another point in favor is represented, as mentioned earlier, by the fact that Golgari Midrange is the second most played deck and that the matchup is strongly in favor of Dimir Midrange. On top of that, the gameplay of the archetype is very flexible: by playing black we have access to some of the best (if not the best) removals of the format; by playing blue we can afford to have a package (albeit reduced) of counterspells and instant speed plays (in this case almost all blue creatures).
The deck is able to play while waiting for the opponent’s moves in most turns and this is a big advantage for a deck that can afford both to attack and control the game. I think "flexibility" is the key word of the deck: we can play creatures in our opponent’s turn, we can counteract our opponent’s spells, we are well equipped with removal spells, we have creatures that can generate a lot of value, we have a planeswalker who wins the games if he stays on the field long enough and we have a chance to keep drawing once our resources are exhausted.
If we compare the playstyle to that of Golgari Midrange for example, we notice that on the other side only some of these game possibilities are available. Golgari, not having the blue color available, has no way to use counterspells effects or play creatures at instant speed. On the other hand, Golgari is able to remove artifacts and enchantments with greater ease, generate more life points and anticipate some plays (Llanowar Elves).
Although the strategy is for both of them the Midrange one, the way it is implemented is very different among the two decks. This also helps us to understand how balanced the format is at the moment and how difficult it is to have a clear preference regarding the list and archetype to play.
Conclusions
Although the format is currently balanced, I think that Dimir Midrange represents a relevant certainty. At the same time, I don't think it's the easiest deck to play, especially in some matchups. Duskmourn has greatly helped this archetype with both the released lands and Enduring Curiosity or Kaito, Bane of Nightmares. The possibility of never being left without resources, which now the deck has also thanks to these two additions, has compensated for one of the previous shortcomings of the archetype. In short, if you have an important event in Standard format, I think that Dimir Midrange is definitely the safest choice to make.