Tiki Adult Build and Sugestions

You say 'nuke', but your Tiki, provided she even lives through the first engagement, will have 49 attack and hitting for a 21 damage bonfire on the Vantage turn. That's... unimpressive and will likely miss out on too many OHKO's. That means she gets hit another two times, surely spelling her death.

I don't get why Dark Breath? Your idea is to use Vantage, but Dark Breath doesn't impact defenses. So your Bonfire hit doesn't get boosted.

Also, this is a one trick pony, as after the first Bonfire hit, she has too little hp left to engage and no special ready to Vantage effectively.

Deflect melee seems very redundant, as you will have 42 physical defense. It also only helps against brave/desperation users, and you probably shouldn't let Tiki tank blue's with those skills anyway.

I get that building off meta builds is cool and I try it all the time myself, but this one seems unrefined.

May seem like i am only pointing out the negative, so let me try to give some advice.

Try using Light Breath instead. You can provide meaningful buffs to allies by attacking, and you make Tiki way more tanky on enemy phase, too. If you can dance her, then she gets a 5-point attack boost for her special charged attack.

QR3 seal is obviously good for her, possibly letting you replace Bonfire with Ignis, but that's probably too meta for you. Instead, you could try to use Brash Assault. Attack something with enough damage to get you below 50%, kill it with vantage next turn, and now you have Tiki capable of doubling melee enemies on player phase. Has nice synergy with the Light Breath/Dancer combo above, too.

My two cents!