Hmmm, I am not too sure that only fire status protection is good enough in FSC. I think most of the fire in FSC deals elemental damage first ( all except zombie breath ), then you get fire status.
To support my suggestion Crest of Almire has the best fire status defence but still breaks from 2 hits from all FSC fire (except zombie breath). I don't have numbers how good elemental defence protects you though.
I also think that Vana deals pure fire damage(no elemental) since Crest of Almire can withstand his hit(not having elemental defence), but Ancient Plate Shield can't(having so much normal defence).
Edit:
"Damage dealt by attacks imbued with the fire, shock, or freeze status conditions contain elemental damage; " from wiki. So any fire/shock/freeze does an elemental damage regardless of your fire protection.
@Mawashimono
Sword damage bonus is good, but don't forget that speed is important to interrupt zombie attacks. Especially if you use second swing of DA it is either you interrupt zombie or zombie interrupts you. If you get Snarbolax set as Bopp already said the best UV would be fire status defence IMO, because even zombie hits can put you on fire, needless to say that fire can interrupt your charge.
Just to clarify, fire damage is not elemental. Elemental armor does not lessen the damage from fire; only fire armor does.
The undead and fiends in FSC deal normal and shadow damage. The Slag Guards and Vanaduke deal normal damage. So yes, you want normal, shadow, and fire. In choosing Vog Cub vs. Snarbolax, you have to consider whether fire or shadow is more important. I would say fire. You also have to consider attack speed vs. damage. Both are desirable, but many people use DA, because it has a big swing and big knockback, and hence is great against crowds of zombies. For DA, Vog Cub's attack speed boost is very helpful. If you use, say, Glacius, then the damage boost might be more useful.
A Snarbolax set with high fire UVs would be pretty nice. Armor of the Fallen is great, except for its damage penalty against fiends (trojans).