From the Malifaux Tactica Wiki:
Oiran are the Ten Thunders escorts in Malifaux. They understand the power of words, and find their place in the city by whispering secrets and lies, twisting others to their objectives.
Oiran only have their Concealed Weapon, which is close range. If Oiran is Harmless when they make a Concealed Weapon Strike, you can choose to add a positive flip to either the attack or damage flip, which helps them out a lot.
Oiran are Harmless, and have two ways to regain Harmless after they have lost it, (1) Sultry, and a Cb trigger for killing a model with Concealed Weapons.
Expert Defense improves the benefits of taking a Defensive Stance, giving Oiran an extra positive flip, and only reduces walk and charge by -1/-1.
The Defensive Dance trigger allows Oiran to assume a Defensive Stance after casting Tranquil Dance for a 6+ mask. If you have the card to spare, this allows you to buff your crew or debuff the opponent, if in range, while still protecting Oiran.
If fighting a Wp duel heavy list, keeping models around Oiran can be very useful. She can (0) Appealing to give Wp +1, and (1) Tranquil Dance can give a positive flip to Wp Resist Duels to models within 6".