Most played cards in The Perfect Storm:

2 Decks
Polluted Delta
8 copies - 4 average
Dark Ritual
8 copies - 4 average
Force of Will
8 copies - 4 average
Brainstorm
8 copies - 4 average
Duress
8 copies - 4 average
Hurkyl's Recall
7 copies - 3.5 average
Underground Sea
6 copies - 3 average
Bloodstained Mire
3 copies - 1.5 average
Tendrils of Agony
3 copies - 1.5 average
Phyrexian Negator
3 copies - 1.5 average
Red Elemental Blast
3 copies - 1.5 average
Xantid Swarm
3 copies - 1.5 average
Chain of Vapor
3 copies - 1.5 average
Tinker
2 copies - 1 average
Tolarian Academy
2 copies - 1 average
Timetwister
2 copies - 1 average
Ancestral Recall
2 copies - 1 average
Vampiric Tutor
2 copies - 1 average
Mind Twist
2 copies - 1 average
Time Vault
2 copies - 1 average