First off, I am assuming you're not negelecting rows? I know deads are good for mass back developement, ie: lumbar, and erectors plus traps, but rowing and or chinning of some kinds hit the back in a differing way only exclusive to drawing the arms towards the torso.
Anyway, your core so to speak, is getting trained (at least) statically, thru deads and squats to an okay extent.
That said, if you are looking for training of the ab and maybe low back thru flexion and extension, what about Russian twists, hanging leg raises, roman chairs, even bw only hypers?
Last question, do you spilt your body parts up like that because of time issues, or preferences or what? Just curious!?!?