check for return air leaks in the attic. test the temperature difference between the return air grill and the entering side of the evaporator. if you have electric heat, you will need to take the second reading at the entering side of the unit. if it's ductboard, poke a hole; if it's metal duct, drill a hole in the duct there. if you have a gas fired furnace, measure the intake of the evaporator by making a hole in the transition just prior to the coil entering side. if the ducts on the return side of the coil are not well sealed, the intake of attic air has a direct effect on efficiency, of course.
you may want to pay for a second opinion on the functionality of your system. even if you have a hot attic and inadequate insulation, it may run a lot, but you should get some performance out of it. the system needs to be tested thoroughly. home warranty companies do not always have your best interest in mind. that is just a personal opinion.
by the way, the ridge vent is effective, but only if there is adequate intake. make sure the soffet vents at the eaves are not restricted with blown in insulation. the natural draft to draw out hot air depends on a source for outside air at the bottom.