To be fair, quite underpowered. Still using some of the freebie story units.
Also, grats on the assist on my team in clearing the 3rd isle story boss (which is still substantially weaker than Europa by a considerable margin), lol.
In reality, the Frost Dragon is scaled for gear/abilities that are beyond what is currently available outside of TM gear/abilities.
-- If the dragon focuses 2 of its 3 attacks in a single round on the same caster, the caster is dead (it can do over 1000 per hit, even with Cheer up).
-- The dragon has a massive HP pool. So massive, that any damage below 10k per offensive unit per round might as well be 1 damage.
You can't use items in the Colosseum, so no ethers to refill MP.
So, assuming 3 offensive units at 10k damage/round, 9 rounds are required to kill it. Most units don't have the MP to cast their top spells/abilities 9 times in a round.
At 15k damage/unit, that reduces the time needed to 6 rounds, which is more manageable. But, to pull off that kind of damage requires Full Breaking / Barraging/ Dual Wielding, etc. on top tier units.
So right now, the fight is a pure damage race before the player gets unlucky with attacks from the dragon.
All that for a Turbo Ether recipe? I can wait, doubly so as Turbo Ethers are directly purchasable.