Most played cards in Horde of Notions:

2 Decks
Stomping Ground
2 copies - 1 average
Taiga
2 copies - 1 average
Steam Vents
2 copies - 1 average
Toxic Deluge
2 copies - 1 average
Polluted Delta
2 copies - 1 average
Reflecting Pool
2 copies - 1 average
Savannah
2 copies - 1 average
Temple Garden
2 copies - 1 average
Tropical Island
2 copies - 1 average
Watery Grave
2 copies - 1 average
Windswept Heath
2 copies - 1 average
Wooded Foothills
2 copies - 1 average
Swords to Plowshares
2 copies - 1 average
Verdant Catacombs
2 copies - 1 average
Eladamri's Call
2 copies - 1 average
Lotus Cobra
2 copies - 1 average
Plateau
2 copies - 1 average
Abrupt Decay
2 copies - 1 average
City of Brass
2 copies - 1 average
Command Tower
2 copies - 1 average