Yes you should have the noc code with noc job discriptions on your emplyer letter, I asked my employer to mention all the details I needed and it was specificaly for immigration, my letter letterally say (attn Immigration and citizenship) Normally its standard practice to indicate the duties from the NOC list. The noc list is so broad that we have to use it. The noc list is used to place your occupation on the immigration application.
hope this helps
It's nice to have it but is not a must.
What's more important is to have job description that matches your NOC code.
I didn't have NOC code on my reference letter and it was never a problem during the application process.