Do we really mean N1? N2 governing is what our day to day existence is based on. N1 governing just ensures the engine keeps running after the start sequence is completed.
212man - I'm with you on this. Perhaps there should be a distinction between single and twin operation here and what we are trying to diagnose in terms of failures.
A torque split might be the first indication of a governor runup or rundown or engine failure but the Nf and Nr relationship will be the easiest (often bigger gauges) to assess, especially with a triple tacho (two Nfs and an Nr needle). Teaching for us has always been to use the triple tacho for diagnosis and reaction (if any required) and use PTIT/T4/T6 and N1/Ng as confirmation.