One of the key symptoms of a stall is a high ROD
are you sure about that?
YES.
1) Specifically:
That quote is from a paragraph I wrote regarding PPL level stalling.
It is very possible to stall and be climbing/descending/high speed/low speed. And in any attitude.
and 2) Generically:
If recovery action is not taken, even a stall (as opposed to an approach to a stall) entered from any flight mode will, fairly quickly, result in a high RoD - possibly with the added bonus of auto-rotation.
If you are teaching high RoD as a symptom of a stall you are misleading your students. Now a spiral dive does produce a high RoD and if you are teaching high RoD = stalling then guess what the student will do?
Of course a dive will result in a high RoD. Forget students, probably every human on earth could understand that.
BUT:
Climb Attitude: Gaining height = Climb; whereas High RoD = Stall
Slow Flight Attitude: Level Flight = Slow Flight: whereas High RoD = Stall