I'm sorry, but that comparison is off. Grace is a pretty popular secondary character, with multiple appearances across several quests and stories, while these three were literally just added to the game, so the warehouse isn't just full of dudes.
I didn't mean her entire storyline, I meant literally just her first few scenes. By the end of Grace's first scene, we have a outstanding grasp on her character: a former party girl trying to still hang out with her friends and talk about meaningless stuff like horror movies that is constantly being torn away to the slightly ill-fitting roles of struggling small-business owner and mother figure to Eve. By the end of her second scene we've reinforced this conflict: she overslept and couldn't watch the store due to her own negligence, but still tries to play the authority figure to Eve cutting class despite not being able to live up to the responsibility herself. Having her play off other characters like Eve, Tuuku, and Odette rather than being one big expository dump really helps, too, even though we're introduced to two of them at the same time as her and we've only barely gotten to know Eve.
Meanwhile, what do we get from Khadne's first scene? Well, she's learned to speak a little English. And she knows how to make vodka from her dad's yak milk recipe. And she comes from Khakassia, which is cold and boring, and she ran away and got sold into sex slavery, which also sounds kind of boring. And now she makes vodka for Nadya. And she's wondering why you're asking so many questions, in a game that literally gives you a list of questions to ask her. And....
She never directly interacts with another character after that. Her next and basically last scene is that there was a vodka blowup and now she's sad, so Nadya needs you to give her sexy times to make her happy again. That's Brazzers levels of porn writing. Katya isn't much better, either.
My question is, why the hell are they even in the game? Why couldn't the time and effort it took to make their assets and sex scenes have been spent building up a singular character like Svetlana that could fill multiple roles for a small update? Y'know, like they did with Consuela? Instead of one strong character with four or five animations and several scenes, we got three weak ones with one or two scenes/animations. In the immortal words of Ron Swanson: