I have been using all stock stuff in my ITB car, and never broke one. Any chance that something is misaligned, or that you are being especially harsh with launches or gear changes? Moving to the stiffer stock mounts (from a diesel?) will reduce the deflection and wear. I would not go solid, even on my race car. It is beneficial to isolate drive train vibration from the rest of the chassis, to keep things from vibrating loose, and limit fatigue loading of mounting points.
Recent rules changes have me looking at making something lighter an stiffer, but there is a lot in front of that item on the list.