I've featured one of Craig Rocco's decks before and noted that he's always up to something different, but this one is even more out there than normal. It took me awhile to break it down, but I think I see what's going on here.
Fundamentally, this is an Always Watching deck. It may seem strange to build around the card rather than use it to supplement an already strong aggressive deck like R/W Vehicles, but it's really quite good right now. It helps you punch through Ishkanah, Grafwidow and makes your creatures match up very well with those in W/U Flash.
The latter effect is substantial because being able to keep the W/U Flash deck on the backfoot means they won't be able to effectively leverage their flash cards, instead acting first so they don't fall too far behind.
And when your opponent is scrambling to catch up on the battlefield, Verdurous Gearhulk is there to shut the door. Creatures like Loam Dryad and Thraben Inspector that are made into solid bodies by Always Watching are suddenly huge threats after some help from a Gearhulk. The goal here is to absolutely dominate combat, and the tools are there to do it. In particular, the choice of Noose Constrictor is an important indicator since it lets you sacrifice material to make combat difficult for your opponent.
You also see a complete lack of removal in the main deck beyond Reflector Mage so dominating combat is absolutely essential. Blossoming Defense instead takes the space for non-creature spells and it's a great tempo play against the common removal spells in the format, although don't overlook its ability to blow out a key double block on one of your important creatures.
The one questionable card to me is Nahiri, the Harbinger. I don't see how it fits in with what the rest of the deck is doing, whereas a more traditional card like Tamiyo, Field Researcher looks great. The major plus in Nahiri's favor is the ability to play it ahead of schedule, usually on turn 3, and then ultimate it on turn 5 to find a second copy of Verdurous Gearhulk, which should be an absolutely devastating play.
Tempo decks that don't have a lot of card advantage do want to have a powerful killing blow like that, and with twelve sources of mana of any color, splashing is reasonable in this deck. And if I know Craig, there is always a method to his madness, although sometimes I wish the balance would tip more toward the former than the latter.
- 4 Verdurous Gearhulk
- 4 Loam Dryad
- 3 Noose Constrictor
- 4 Reflector Mage
- 4 Servant of the Conduit
- 4 Thraben Inspector