The problem with Asuka is that she broke away from her archetype far too early. She was very clearly supposed to fill the bratty "Ojou-sama" niche on the roster, but no longer fits the bill. She can't act high and mighty after repeatedly getting piped in a public restroom, and she's not really tsundere after openly confessing her love for MC. So she kind of lost her identity.The reason I don't like Asuka is because she's so clingy to the MC, so submissive. He doesn't want to have sex with her all the time, but she wants to have sex with him. She is a pathetic bitch, without a spine, without self-respect. That's why she is absolutely dispensable for me. She is just good for being a doggie on a leash, some sort of Paris-Hilton-Chihuahua.
But you are right, maybe she is good at tapping her mother for informations and passing them on to the MC.
So: No Kill but to drill!
Motoko is the better rich girl, Yoko is the bigger brat. I guess Asuka was meant to be the middle ground between those two, but ultimately just turned out kind of pathetic.