Most played cards in Mardu:

2 Decks
Night's Whisper
8 copies - 4 average
Kor Skyfisher
8 copies - 4 average
Chainer's Edict
8 copies - 4 average
Prophetic Prism
8 copies - 4 average
Lone Missionary
7 copies - 3.5 average
Terminate
7 copies - 3.5 average
Flame Slash
7 copies - 3.5 average
Rakdos Carnarium
6 copies - 3 average
Pyroblast
6 copies - 3 average
Gorilla Shaman
5 copies - 2.5 average
Palace Sentinels
5 copies - 2.5 average
Ash Barrens
5 copies - 2.5 average
Magma Spray
4 copies - 2 average
Electrickery
4 copies - 2 average
Wind-Scarred Crag
4 copies - 2 average
Scoured Barrens
4 copies - 2 average
Shrieking Grotesque
4 copies - 2 average
Radiant Fountain
3 copies - 1.5 average
Thraben Inspector
3 copies - 1.5 average
Bojuka Bog
3 copies - 1.5 average