Does Focus adds to damage from elemental skills, such as the Berserker's Shadow Burst or Frost Breath?
If a skill says
So if you're going to use a lot of skills that mention Elemental Damage, it makes sense to invest in the Focus stat. Even so, my Outlander uses only skills with elemental damage and only has Focus points invested.
It's also easy to verify this (if you don't mind using the console on a test character).