I would have to disagree, a rear coil over suspension retains a straight axel. Albeit, if an independent rear set up was used, I couldn't imagine doing so without a coil set up.
i just cant think of where on a solid axle you get torque except in the center. ohh just figured it out you would have to run a L shaped bar parallel to the axle and have one end secured to the axle and one to the body.
Im having a hard time fully understanding your statement but if you dont believe that an IRS could have torsion bars check the porsche 944 stock set up.