Painter relies heavily on the highpoly-baked-to-lowpoly workflow, while in archiviz you tend to just render the highpoly assets directly. Depending on how you like to set up your models and materials, you may or may not like to use painter for archiviz. Painter can be useful to create imperfections, a little bit of dirt, decals, etc, but it won't replace Designer and/or Photoshop by any stretch of the imagination.
That said, it's really easy to learn, so you'd be remiss not to learn it if you already own the license.