I agree. I think that the only exception to this would be Penelope/Lindsey that IMO started out as secondary characters but really grew on me and i can't see the game going forward without them in it. Sure, they're not on Chloe/Nora/Lauren/Emily ( i really don't like Emily but i can't negate her importance to the MC's story so...) level of importance to the plot but they have a solid role. Lindsey was necessary to build on the whole frat dispute thing and Pen, well i thought initially that seh was going to be the uptight one, and not only about sex but as her personality, but she really grew on me with the whole "hacking to help and almost fucking everything up", the porn game dev bit, her "Fuck the Police" mode when at the concert...But the thing is side-chicks are getting more screen time than main girls for some reason. I guess different writers are the problem they all have different vision with the girls.
I'd put those 2 right beneath Nora/Chloe on my Tier List, Nora being my #1