Most played cards in Mardu:

1 Decks
Night's Whisper
4 copies - 4 average
Kor Skyfisher
4 copies - 4 average
Chainer's Edict
4 copies - 4 average
Prophetic Prism
4 copies - 4 average
Lone Missionary
3 copies - 3 average
Terminate
3 copies - 3 average
Duress
3 copies - 3 average
Pyroblast
3 copies - 3 average
Palace Sentinels
3 copies - 3 average
Flame Slash
3 copies - 3 average
Thraben Inspector
3 copies - 3 average
Gorilla Shaman
3 copies - 3 average
Orzhov Basilica
2 copies - 2 average
Rakdos Carnarium
2 copies - 2 average
Scoured Barrens
2 copies - 2 average
Radiant Fountain
2 copies - 2 average
Bloodfell Caves
2 copies - 2 average
Raven's Crime
2 copies - 2 average
Magma Spray
2 copies - 2 average
Electrickery
2 copies - 2 average