Ghost ; I'll go for Dendrobium 1st choice and Iono 2nd choice.

Dendrobium has 100% re-act + double rate use of her own active skill is super powerfull.
She has highest HP compare to other 2, but have most less ATK & Def.

Iono has highest DEF and can re-act but only 40%.
She's dodge unit, you will need her for broken map.

Onibus (Victoria) has highest ATK.
Her double rate use of everyone active skill when she got hit is good.
But it won't work well if your team don't have enough girl to boost base active skill rate use.