Dejnovs thunder team confused me, but maybe im just not making best team of that element. Seems they'll be really good for content where u need to survive for long periods though.

My opinion Fire: Uriel A, Vahagn, svarog A, BF amon.
Imo fire is all about fast burst, and as my current team, it makes herc the bottleneck for how fast it can go.
Vahagn is not to be underrated here, as she gives herself 5 turns vigor and guaranteed triple attack, making urielA legit the only thing faster than her that doesnt instafill their gauge.
BF amon makes the team faster(20 bg to team), gives a little survivability (20% 3t dmg cut), and gives 20% atk, AND 50% elemental atk (3t each), to the whole team. Combined with stacks of svarogs atk buff, vahagns vigor boost + uriel and her burst dmg buffs, get shitloads of damage.

Again only my opinion on the ideal fire team. Mtix worthy is fire frey, because she packs 30% fire res down, and is also very fast, with the ability to ramp up her own burst damage.