First of all, we'll need to trim the deck down to 30 cards to increase consistency.
Then we'll get rid of some cards which don't quite fit in with the strategy of Vampire masteries. The three Black Dragons will be the first to go, followed by three of the Obsidian Pillars, two Steals, two Devourers, and a Drain Life.
In their place we'll add two Emerald Pillars, three Adrenalines, a sixth Minor Vampire, and a Dagger. We'll also change the mark to Life.
The Adrenaline (mostly fuelled by the mark) has a very nice synergy with the Vampires by allowing them to gain multiple life-draining attacks per turn, and the Dagger is some more free damage that also serves as Steal/Deflagration bait so that your other permanents are protected.
The final decklist looks as follows:
Mark of Life
1 Dagger
2 Emerald Pillar
3 Adrenaline
11 Obsidian Pillar
2 Devourer
1 Dusk Mantle
1 Steal
1 Nightfall
2 Drain Life
6 Minor Vampire