Most played cards in Mono-Red Thermo-Alchemist:

2 Decks
Hanweir Garrison
8 copies - 4 average
Thermo-Alchemist
8 copies - 4 average
Collective Defiance
7 copies - 3.5 average
Weaver of Lightning
6 copies - 3 average
Rending Volley
6 copies - 3 average
Incendiary Flow
6 copies - 3 average
Roast
5 copies - 2.5 average
Thunderbreak Regent
4 copies - 2 average
Chandra, Flamecaller
4 copies - 2 average
Evolving Wilds
4 copies - 2 average
Draconic Roar
4 copies - 2 average
Exquisite Firecraft
4 copies - 2 average
Galvanic Bombardment
4 copies - 2 average
Tormenting Voice
4 copies - 2 average
Impact Tremors
4 copies - 2 average
Fiery Temper
4 copies - 2 average
Dance with Devils
4 copies - 2 average
Fiery Impulse
3 copies - 1.5 average
Hanweir Battlements
3 copies - 1.5 average
Drownyard Temple
3 copies - 1.5 average