My Parkzone Albatros doesn't seem to want to bank at all with rudder only; maybe this is because it's got little to no dihedral. In fact, the top wing seems to have a little anhedral.

"Absolutely all of my model aircraft bank/turn just fine with no rudder input whatsoever."

I'm pretty sure that statement is accurate, within the context of the models a person has. I have five right now, and 60% of them can't turn at all without a rudder-the are 3 channel and don't have ailerons!!!!