there's a love here of the torso, and i think that's part of the flattening that helm's pointing at, but i think that bothers me less than that the rest of the form seems less considered/constructed. the appendages, hips and, to quote anchorman, "crotchal region" come across as a bit more ball-and-tube than anatomical.
There's something about the composition too that's more than lopsided, it speeds across the left and then, finding nothing substantial on the far right, continues off the page. there needs to be some kind of anchor or, if the last head is supposed to be bright, make it brilliant and bring in more darks to counterbalance (with her taking a slight darkening too, or at least more contrast).