Most played cards in 4c Delver:

3 Decks
Daze
12 copies - 4 average
Force of Will
12 copies - 4 average
Lightning Bolt
12 copies - 4 average
Scalding Tarn
12 copies - 4 average
Brainstorm
12 copies - 4 average
Polluted Delta
12 copies - 4 average
Tarmogoyf
12 copies - 4 average
Ponder
12 copies - 4 average
Delver of Secrets
12 copies - 4 average
Tropical Island
9 copies - 3 average
Wasteland
9 copies - 3 average
Abrupt Decay
9 copies - 3 average
Oko, Thief of Crowns
9 copies - 3 average
Thoughtseize
8 copies - 2.67 average
Pyroblast
8 copies - 2.67 average
Surgical Extraction
6 copies - 2 average
Veil of Summer
6 copies - 2 average
Volcanic Island
6 copies - 2 average
Plague Engineer
6 copies - 2 average
Underground Sea
6 copies - 2 average