Most played cards in Dark Depths:

6 Decks
Thespian's Stage
19 copies - 3.17 average
Dark Depths
19 copies - 3.17 average
Urborg, Tomb of Yawgmoth
17 copies - 2.83 average
Vampire Hexmage
16 copies - 2.67 average
Mirage Mirror
15 copies - 2.5 average
Thoughtseize
14 copies - 2.33 average
Grafdigger's Cage
12 copies - 2 average
Expedition Map
12 copies - 2 average
Leyline of the Void
12 copies - 2 average
Ancient Tomb
11 copies - 1.83 average
Wasteland
11 copies - 1.83 average
Pithing Needle
10 copies - 1.67 average
Null Rod
9 copies - 1.5 average
Mental Misstep
8 copies - 1.33 average
Mindbreak Trap
8 copies - 1.33 average
Dark Confidant
7 copies - 1.17 average
Black Lotus
5 copies - 0.83 average
Strip Mine
5 copies - 0.83 average
Mox Jet
5 copies - 0.83 average
Demonic Tutor
5 copies - 0.83 average