Most played cards in Vampires:

2 Decks
Marsh Flats
8 copies - 4 average
Kalastria Highborn
8 copies - 4 average
Gatekeeper of Malakir
8 copies - 4 average
Bloodghast
8 copies - 4 average
Vampire Hexmage
6 copies - 3 average
Lightning Bolt
4 copies - 2 average
Memoricide
4 copies - 2 average
Blackcleave Cliffs
4 copies - 2 average
Lavaclaw Reaches
4 copies - 2 average
Dragonskull Summit
4 copies - 2 average
Relic of Progenitus
4 copies - 2 average
Pulse Tracker
4 copies - 2 average
Thoughtseize
4 copies - 2 average
Vampire Nighthawk
4 copies - 2 average
Vampire Nocturnus
4 copies - 2 average
Grasp of Darkness
4 copies - 2 average
Burst Lightning
4 copies - 2 average
Vampire Lacerator
4 copies - 2 average
Mark of Mutiny
3 copies - 1.5 average
Dark Tutelage
3 copies - 1.5 average