Don't fall into the trap of mis-diagnosing low oil pressure as a failure in itself when it is often simply a result of the engine having already run down. Turbines will run for some time on hardly any oil pressure, provided that some oil is still in the system.
Obviously a relight must NOT be attempted if any of these indications are present.
True, but in the case of the mentioned PT6, the prop will feather with a loss of engine oil pressure.
When at a previous company we had a PT6 on a Twin Otter go from about 10-15# of torque to seizure in the blink of an eye. Thankfully it wasn't during the climb when at 40# of torque.