I actually prefer qum if I want to use the whip+handcuffs combo.
That said, I do stick a buttplug on Yarra for the most part.
It's just, her single target damage is terrible even against enemies weak to sex attacks, and her actual strong attacks drain her lust pool dry in 2-4 fights unless you drag them out so she can use her recovery skills. It's not like she recovers all that much lust on her own like Nalili and her 5 lust for every time/target she attacks either, she basically needs to lust renewal herself every other fight.
If every single enemy in an area is weak to sex I might use her for incubus king's emissary, but even than I'll usually swap her out after a few fights because it's too much of a hassle to regen her lust pool.
her status affects on haze of lust are pretty useful if enemies are vulnerable to them though, but I basically stop using Yarra in general after Altina joins unless she's forced into the party(including multiple party spots) or I'm in a section where I can't rest to restore mana and just want some sexual mana or a lust renewal on nalili.
That said I haven't really played around with her synergy skills because of that.