I just recently overcame this problem and I'll tell you what I did. I started viewing my hands as hooks to hold the weight and began pulling with my elbows if that makes sense.
Here are a few excellent tips I can give you to make sure you feel it in your back.
1) When doing pulldowns, pullups, or rows visualize pulling the bar apart. You need a decent, deep grip to do this, but pull the bar apart. By pulling the bar apart you keep your form in check and get a tighter contraction of the muscles surrounding the scapulae (Rhomboids, Traps, and Lats). In all honesty, you should be pulling the bar apart on benches during the downward motion as well to help stabilize yourself and engage your lats to keep tension in the bar.
2) Minimize any and all leg involvement during your sets unless you're purposefully cheating and can CONTROL it. Jerking the weight up will not allow you to feel the muscles in your back doing the work and is a good way to injure something.
3) Perform your all of your warm-up sets slowly with correct form to help yourself get used to the feeling of pulling your scapulae back.