Most played cards in 4c Midrange:

2 Decks
Disenchant
8 copies - 4 average
Swords to Plowshares
8 copies - 4 average
Serendib Efreet
8 copies - 4 average
Tundra
8 copies - 4 average
City of Brass
8 copies - 4 average
Mishra's Factory
8 copies - 4 average
Lightning Bolt
8 copies - 4 average
Red Elemental Blast
7 copies - 3.5 average
Chain Lightning
5 copies - 2.5 average
Counterspell
5 copies - 2.5 average
Blue Elemental Blast
5 copies - 2.5 average
Strip Mine
5 copies - 2.5 average
Volcanic Island
5 copies - 2.5 average
Savannah Lions
4 copies - 2 average
Psionic Blast
4 copies - 2 average
Plateau
3 copies - 1.5 average
Fireball
3 copies - 1.5 average
Control Magic
3 copies - 1.5 average
Shatter
2 copies - 1 average
Divine Offering
2 copies - 1 average