Grixis always seems like it's on the edge of playability. There are clearly good cards available, but Sphinx's Revelation tends to overshadow them. However, this deck blends some of the best aspects of Mono-Black Devotion and U/W Control together.
For starters, we have an actual clock. Grixis is notorious for not having inevitability. Eventually, something will slip through the cracks and you won't have the right answer for it. Additionally, you are susceptible to burn decks going long due to the lack of lifegain.
Instead of playing the U/W Control game, Grixis decks should focus on what they're doing best, and that's typically beating other control decks. Drawing cards with Sphinx's Revelation is great and all, but wouldn't you rather be Rakdos's Returning them for their hand instead? I like how this deck embraces that role and runs with it, aside from the Elixir of Immortality, which does little aside from gain you some life.
Just because a deck isn't a major player doesn't mean it will never show up. After all, every deck, even Mono-Black Devotion, was just a brew at some point.