Dear Jimbo,
I understand what you are saying.....I do not disagree, but I think that even though there is more sq ft of sofitt perhaps, there may still be less resistance from the closer ridge vents is some cases.
As to the backdraft situation, it has actually happened and is not too much of a stretch. I've inspected many homes where just having the bath vents and exterior exhausting range hood going caused a backdraft situation on a gas water heater or furnace. You could actually see it fogging a mirror when held next to the draft vent of the heater. With homes being tighter now it happens easier then when homes were more drafty.
As you asked, here are some interesting articles on the subject of not using powered attic ventilators.....
Home Energy Magazine :: Drawbacks Of Powered Attic Ventilators
Advanced Energy
http://tinyurl.com/66qq8jv
Hope you enjoy them, they are interesting.
BTW, I think the solar tubes are great in some homes, as long as they are quality ones and installed properly so as to not cause a roof leak.
Respectfully, Frank