It should rev higher. This is not normal. Could be a faulty temp sensor - that's a cheaper thing to replace than ECU.

Warm up time on a cold day - I've tried:

1. warming up 3 mins before driving off.
2. warming up 30 sec before driving off.

The smoothest ride is had with (1).
I don't mind investing 3 mins in warm up.

I wonder what is warm up time for some of our diesel engined forum members.