As a general rule of thumb, azerite traits that add dmg or healing to a skill stack. However any resource gain or percent chance to trigger something do not stack.

Do all Azerite traits stack?

Azerite trait stacking is a good thing, and almost all traits are stackable. And remember, you can check bloodmallet to see how much each stack of an Azerite trait is worth for your specific spec. You can also check trinkets on there!

Do Azerite traits stack 2020?

Do my traits stack if I get more than one? Every Azerite trait in the game stacks in some capacity. Specifically the following aspect of each trait stacks: Damage and healing increases, stat increases.