A torque display failure would be a non-event if the ATPCS is not armed. Auto-feathering does not occur and the actual torque is completely unaffected. In these cases, it is nothing other than an inconvenience. The only real critical phases are with ATPCS armed. i.e. From takeoff power selection until the PWR MGT is moved out of takeoff thereby disarming ATPCS. The only other likely phase is during a go-around for similar reasons.