Most played cards in Mardu:

3 Decks
Bloodstained Mire
12 copies - 4 average
Draconic Roar
8 copies - 2.67 average
Thraben Inspector
8 copies - 2.67 average
Unlicensed Disintegration
8 copies - 2.67 average
Smuggler's Copter
8 copies - 2.67 average
Battlefield Forge
8 copies - 2.67 average
Scrapheap Scrounger
8 copies - 2.67 average
Toolcraft Exemplar
8 copies - 2.67 average
Inspiring Vantage
8 copies - 2.67 average
Concealed Courtyard
8 copies - 2.67 average
Kolaghan, the Storm's Fury
6 copies - 2 average
Fiery Impulse
6 copies - 2 average
Kolaghan's Command
6 copies - 2 average
Caves of Koilos
6 copies - 2 average
Hallowed Moonlight
4 copies - 1.33 average
Tormod's Crypt
4 copies - 1.33 average
Declaration in Stone
4 copies - 1.33 average
Shrapnel Blast
4 copies - 1.33 average
Siege Rhino
4 copies - 1.33 average
Windswept Heath
4 copies - 1.33 average