This is my updated Temur Midrange deck. I focused on hard-to-remove fatties and countermagic. There is more of a blue splash in this deck than other popular Temur lists.
This deck is very powerful with acceleration into Polukranos, Stormbreath, Knuckleblade, and Ashcloud Phoenix. Countemagic adds an interesting element. Instead of trading your big threats for removal or removing your opponent's creatures, you're able to counter the spell without affecting the board. The deck feels extremely powerful with many fantastic draws, consistent mana, and decent matchups across the board. The downside is its fragility - sequencing spells incorrectly or casting say, a Temur Charm fight instead of holding a counter can and will cost you the game.
This deck has decent matchups against Jeskai and Mardu. In regards to Jeskai, the dice roll matters a lot. They have a number of hands which just beat us, so play/draw order matters a lot. The key is to play more than one spell a turn since they 1:1. Mardu can tear us apart with hand disruption and removal (Stubborn Denial/Disdainful Stroke are the best cards against them). The control matchup is a bit iffy, especially if they're playing perilous vault (haven't played it much). They can eek out wins with seeker/butcher lifelink. Their big weakness is playing one spell a turn until T5-6, so being able to drop a fatty with counterspell backup is huge. Abzan has been a huge problem and has prompted the most change to the deck.
As it stands, Abzan hoses me more often than not (it seems dependent on whether or not they draw well, which they probably will). I think that playing a more controlling game is the way to go, but that also means letting them resolve kill spells on my creatures so I can counter spells that strongly affect the game, like Elspeth, Siege Rhino, and Wingmate Roc. Dig Through Time, Windstorm, and Aetherspouts are specifically for them. Sagu Mauler is also impossible for them to deal with save for Elspeth or End Hostilities.
Aggro matchups are ok. I added Anger to the board and Magma Sprays and Barage of Boulders are always an option. U/W heroic is tough. Ferocious probably won't be enabled for the T2-3 enchantments and the creatures are out of Anger/Lightning Strike range after a turn. Back to Nature would hose them hard. Stormbreath is also a great blocker so long as they don't have Aqueous Form cast.
