I think Fire has quite a few options against us but Fire works best by itself. Fire could need a lot of Pillars (unless it's Immolation deck). An effective deck could be 9 Earth Pillars, 5 Earthquake, 1 Pulverizer with 15 Gravity cards.
Now of course Fire could use Enchant Artifact with Earth mark to power Golems but Enchant Artifact isn't really something that is exclusive for Gravity. But it could also be an Immolation deck which can bring in annoying rainbow elements like Freeze.
The real problem with Fire is Rage potion. We could counter that with Momentum for our Fire Eaters....
I don't really see one counter for Fire.