Hi FlexKitten - your back routine looks good. Do you mix it up every 6-8 weeks or so? Your muscles can adapt easily to the load/exercises you are giving it. I don't think its neccessary to work your back more than once a week personally. But it depends on the effectiveness of your current workouts. Have you tried adding weight to your pullups? Or resistance from a partner on these? Don't forget your shoulders!! If your shoulders aren't developed, your V-taper won't look complete.
You can also try alternating light and heavy weeks...I've had good results with this. You can go every other week or every third week lighter weights, less sets, more reps. Going light gives your body and opportunity to develop more vascular networks (which means more oxygen, better development/recovery on the heavy weeks), also it helps reduce the body's natural tendancy to slough off those little microscopic tears that we get by going heavy and this aids in overall development.