|Dragonstone units are getting more popular with Weapon Refinery, making their Lightning Breath+ users more difficult to defeat as they gain additional defensive buffs as well as the ability to hit their checks' usually lower Defense rather than usually more dependable Resistance. Normally-built and low-merged Fury 3 Julia can expect to get overpowered by Dragons utilizing Quick Riposte and a variety of Resistance-boosting supplements, including +Resistance refinements, Distant Defense seals, and staying in Defense tiles.
However, by utilizing skills that emphasize Julia's Attack, such as Death Blow 4, Attack +3, as well as using Divine Naga to negate Fortify Dragons defense boosts, Julia can minimize the amount of risk in initiating on dragon units by simply OHKOing them. This build is best used against teams reliant on dragonstone units in both Arena and Arena Assault.
All the provided skills, along with a Hone Attack boost, allow Julia to OHKO even the most magically resistant Nowi (+10 merged with a Resistance boon and refinement, and double Distant Defense 3) in defense tiles. The usually less Resistance-bulky blue dragonstone units, Ninian and Corrin (F), are plainly vaporized. As long as opposing Fae do not bolster their Resistance to an extreme extent and is not in a Defense tile, Julia is also able to OHKO her. If you do face such a specifically-built Fae, a little prior damage from other teammates' skirmishes can put her in range. Additionally, Myrrh gets demolished in similar conditions due to her lower Res bulk.
As for both Adult and Young Tiki, Julia may fall short of one-shotting them by a few damage due to the weapon triangle disadvantage. If they furthermore choose to use Resistance supplements and/or Triangle Adept, Julia thus must rely on a blue teammate to either chip away at Tiki's health or eliminate them entirely. Keep in mind that Julia can power her way through non-Triangle Adept, lower-merged, or less Res-focused variants of the two.
Keep in mind that the aforementioned scenarios and builds are VERY extreme cases; the average player will usually have less merges than +10 and/or favor physically-bulky builds for Fae, Tiki, and Nowi to better tank meta-centric physical attackers such as Brave Lyn. Even in such specific cases, Julia can swim by with competent team support and correct positioning.
Addressing the other parts of this build, G Tomebreaker 3 is a still fantastic option, especially in combination with Divine Naga. Despite this build being player phase-oriented, the likes of fully-buffed Nino, Cecilia, and Gunnthra still can't hope to break through due to both their boosts and doubles being denied. Glimmer has a short cooldown of 2, allowing Julia to break through potentially narrow matchups. Notably, when combined with Quickened Pulse and Infantry Pulse support from other teammates, Julia can enter the battle with Glimmer ready on Turn 1, and can thus actually break through most of the aforementioned Resistance-heavy matchups. Additionally, this combination ensures Julia can nuke most other targets, such as Winter Robin, hard if the opponent doesn’t have a dragonstone unit. Res Ploy 3 is listed for the sake of optimization, though the C slot is perfectly flexible depending on team needs.