Ideas for bad Julia

Well she still is a powerful mage ... 32 Atk + 14 Naga is already 46, which is enough to eat many blues. Her boon / bane hurt her a bit, but she's still very good.

her res is still very decent so she can take many wizardry hits.

IMO you should feed her with a Hinata for a great fury. It'll rise her attack to a neutral status + increase her speed to a correct 33. Maybe a speed seal too. 34 is nice enough to double many blues and archers.

Maybe throw her a glacies / Iceberg instead of her inbuilt draconic aura to compensate for the lack of raw damage. Iceberg being more reliable if she has trouble doubling. With fury + naga (+2 res while attacked) it's a whooping +18 dmg with Iceberg, +30 with glacies.

Summary :

Naga (it would be so sad to drop this one, she's not speedy enough for blades, too frail for TA build)
Movement skill
Iceberg

Fury
Green Tomebreaker (still doubling Ninos, Cecilias and incoming Sonyas out there)
Some C skill your team lacks. BoL is good for budget option