When we discuss general rules we have to remember there are differences between aircraft types and models of those types to take into consideration.
Agreed and that is probably the cause of some of the disagreements.
None of the aircraft I have flown have a governed N1 range, the N1 spools up and down to keep the N2/NF in a governed range. The exception would be the Gazelle but since that is fixed spool, it doesn't count.
In your example, a high Nr with one Nf high would be a runaway up (highside gov failure I believe you chaps with the dodgy president call it). A high N1 and T4 on the same engine would confirm that that one is working really hard and the 'good' engine would have the Nf in the normal range but the N1/T4 back at something like flight idle.
Further confirmation could be made by making a small collective lever movement to note the response - if you lower the lever slightly (not into auto) and the Nr goes up further then you have identified the culprit.