Most played cards in B/R Dragons:

1 Decks
Smoldering Marsh
4 copies - 4 average
Draconic Roar
4 copies - 4 average
Goblin Dark-Dwellers
4 copies - 4 average
Transgress the Mind
4 copies - 4 average
Grasp of Darkness
4 copies - 4 average
Foreboding Ruins
4 copies - 4 average
Cinder Barrens
4 copies - 4 average
Thunderbreak Regent
4 copies - 4 average
Duress
4 copies - 4 average
Ruinous Path
3 copies - 3 average
Read the Bones
3 copies - 3 average
Flaying Tendrils
3 copies - 3 average
Kalitas, Traitor of Ghet
2 copies - 2 average
Ob Nixilis Reignited
2 copies - 2 average
Foul-Tongue Invocation
2 copies - 2 average
Collective Brutality
2 copies - 2 average
Kolaghan's Command
2 copies - 2 average
Dragonlord Kolaghan
2 copies - 2 average
Infinite Obliteration
1 copies - 1 average
Chandra, Flamecaller
1 copies - 1 average