Deck will have 3x mark of fire, 200 hp, and 2x deck size.
Congrats on 1m score then!
Running Firestorms off the mark means that it won't get to play more than about one every two turns, which could let constantly growing creatures or swarms with SoP become a threat. Quinted growers are also possible. Quinted Blue Nymphs and Firebolts could just barely burst enough damage to kill 392 HP, although it's not commonly used against the Arena.
Except for large stalls, especially ones with Eternity, I think this would easily beat most common arena farmers.