Do I need to use a mesh membrane tape (Kerdi Band, etc..) with this product on joints for a waterproof finish?

If your joints are mesh taped and thin-setted, then you shouldn't need to use mesh in the corners with the membrane. At least I didn't.

No it is not required Normally,,,,. But depending on the thickness of the product you are applying it may be required. I suggest mesh if your application is going to be more than 1/4 inch thick.