Midrange decks have had a rough go of it in Modern as of late. Death's Shadow matches their disruptive power while being significantly more efficient and as a result doesn't have to play nearly as many lands, providing important virtual card advantage.
That said, there are two cards that are very powerful in that matchup that midrange decks have used to turn the tides: Snapcaster Mage and Lingering Souls. It may seem problematic to include both of these cards in a base G/B deck, but fetchlands are broken, so why not? Just play the best cards and massage your manabase until it works.
That's what's going on here, with Noble Hierarch coming in to both help fix your mana and accelerate your gameplan, letting you cast Liliana of the Veil on turn 2 or simply curve into a piece of disruption alongside a threat. The opening few turns are so important in Modern and this deck can compete with the best of them there.
The extra color also lets you access the best sideboard cards, with both Ceremonious Rejection and Stony Silence for artifact decks and Countersquall against things like Jeskai Control and Scapeshift which are emerging.
Importantly, what you don't see are the various clunky cards that these decks used to play to win mirror matches. This metagame is not kind to stumbles of any sort, and against the various Tron decks, you need to come out of the gates quickly. The popular decks right now either ignore things like Siege Rhino and Kalitas, Traitor of Ghet or go way over the top of them, so rather than build toward cards that could clog your opening hand, we see four copies of Liliana of the Veil, a card that cuts down on the resources available in the game, which tends to go well for Tarmogoyf.
You can tune this hodgepodge however you like depending on your local metagame, as four colors give you a huge range of options. Just keep the core of great two-mana creatures and one-mana disruption and you'll be fine. Hey, maybe you can go the rest of the way and splash for Kolaghan's Command. In Modern, anything is possible.