The Owner is right, 30-40 cards should be your goal.
You have 10 obsidian pillars, which seems like a lot since each one of those devourers which you will be fractaling serves the same purpose. You will have all that dark quanta and nowhere to put it.
Since devourer serves the same purpose as obsidian pillar, and your mark of darkness creates dark quanta, why not take out all of the obsidian pillars. Starting on turn two you can play one per turn and the longer they are in play the less you need obsidian pillars anyway, so they are useless.
You probably don't need 4 steal, 2 should be enough for now.
A shield or two might not be a bad idea.
Here is how I think I would do it:
6 Devourer
2 Steal
2 Nightfall
1 Vampire Stiletto
3 Minor Vampire
1 Dusk Mantle
2 Drain Life
10 Aether Pillar
4 Fractal
As Many Shard of Gratitude as you have.
I haven't tried that, but conceptually, it should work a whole lot better for you.
Hope that helps