Heck Brian, I'm using a single elevator servo and a nyrod for the elevator on my Swoose. I have used the old torque rods in the past for ailerons but no longer ever use them. The reason isn't because they don't work because if done correctly they work quite well but in this day and age we have such a great selection of servo sizes and prices plus the radios we now have make the torque rods obsolete. I find them more work to set up then the two servo set up and I like being able to adjust and set up the Diff with two servos.
They work and work well but I moved on with the times. If I had a reason to use the torque rods in a plane I wouldn't hesitate, The old school Satyr I'm building is one I would use them on but it's not getting ailerons at all. Three channel is fun too.
Because I have built and flown the Dirty Birdy the thought of using the torque rods would never even cross my mind. It's a big precision plane that will travel at some pretty fast speeds and you could get some control flex with the system.
There were reasons for the single servo torque rod systems back in the day but we have moved way past those reasons today. I wouldn't use the system in the DB but that's just my thinking. The plane will fly with it, not like it's going to fall out of the sky, just better ways to do things. I wouldn't buy a car with drum brakes either but all my drag cars had them and they worked, not well compared to the breaking systems we have today but I didn't die when I had to hit the binders. Went out of my lane a few times though!