Is it common..even when the heater is working

I'll be doing both putting up the curtain, and a portable heater right next to me. Goood ideas! A cold nose. Not acceptable

The short answer is Yes, it can get that cold depending on the outside temps. People often use shower curtains behind the seats to keep the A/C or heat out of the dash, up front where it belongs.

Our engine heater keeps us pretty warm up front down to about 30°F, but below that we run the coach furnace as well while underway. At the other extreme, we also run the generator and roof A/C(s) when the dash A/C can't keep up with the heat.

If I was that cold in the RV, I would crank up the genny and plug in a portable heater right next to my seat.

Cab heaters (and dash air conditioners) in motorhomes are notoriously sad. there is simply too much space for them to handle.
You can try putting up hooks to hang blankets behind the cockpit seating in cold or very hot weather, to limit the space the heater/air conditioner has to try to warm or cool. It might work.
Or, you can try running the furnace while driving, to augment the cab heater.
In hot weather, some people run the generator so they can have the roof top A/C running as they drive.
Remember, in a 32 foot motorhome there is over 2000 cubic feet of air to heat or cool! That cab heater or air conditioner is designed for a truck cab or at best a large SUV!

The heater in our MH keptthe front area comfortable in 28 degree weather-----------which I have only driven in once. By comfortable, I mean no gloves but a long sleeve shirt and possibly an insulated vest.