Most played cards in Doomsday:

3 Decks
Force of Will
12 copies - 4 average
Dark Ritual
12 copies - 4 average
Polluted Delta
12 copies - 4 average
Doomsday
12 copies - 4 average
Underground Sea
12 copies - 4 average
Burning Wish
12 copies - 4 average
Brainstorm
12 copies - 4 average
Flooded Strand
10 copies - 3.33 average
Duress
10 copies - 3.33 average
Chromatic Sphere
9 copies - 3 average
Daze
8 copies - 2.67 average
Orim's Chant
7 copies - 2.33 average
Pyroblast
7 copies - 2.33 average
Tendrils of Agony
6 copies - 2 average
Hurkyl's Recall
6 copies - 2 average
Infernal Contract
4 copies - 1.33 average
Yawgmoth's Will
3 copies - 1 average
Timetwister
3 copies - 1 average
Volcanic Island
3 copies - 1 average
Gush
3 copies - 1 average