Most played cards in Mardu:

2 Decks
Young Pyromancer
8 copies - 4 average
Bloodstained Mire
8 copies - 4 average
Faithless Looting
8 copies - 4 average
Cabal Therapy
7 copies - 3.5 average
Leyline of the Void
6 copies - 3 average
Thoughtseize
5 copies - 2.5 average
Bedlam Reveler
5 copies - 2.5 average
Lightning Bolt
5 copies - 2.5 average
Hymn to Tourach
4 copies - 2 average
Plateau
4 copies - 2 average
Mishra's Bauble
4 copies - 2 average
Wasteland
4 copies - 2 average
Monastery Mentor
4 copies - 2 average
Lingering Souls
4 copies - 2 average
Swords to Plowshares
4 copies - 2 average
Arid Mesa
4 copies - 2 average
Badlands
4 copies - 2 average
Marsh Flats
4 copies - 2 average
Kolaghan's Command
3 copies - 1.5 average
Fatal Push
3 copies - 1.5 average