Most played cards in Humans:

2 Decks
Flooded Strand
8 copies - 4 average
Reflector Mage
8 copies - 4 average
Collected Company
8 copies - 4 average
Windswept Heath
8 copies - 4 average
Thalia's Lieutenant
8 copies - 4 average
Lambholt Pacifist
7 copies - 3.5 average
Dromoka's Command
7 copies - 3.5 average
Disdainful Stroke
6 copies - 3 average
Botanical Sanctum
6 copies - 3 average
Dispel
4 copies - 2 average
Manglehorn
4 copies - 2 average
Glory-Bound Initiate
4 copies - 2 average
Thalia, Heretic Cathar
4 copies - 2 average
Renegade Rallier
4 copies - 2 average
Thraben Inspector
4 copies - 2 average
Tireless Tracker
4 copies - 2 average
Warden of the First Tree
4 copies - 2 average
Canopy Vista
3 copies - 1.5 average
Transgress the Mind
3 copies - 1.5 average
Prairie Stream
3 copies - 1.5 average