This was a problem in the original D:OS as well - 1-handers were always overshadowed by their more powerful 2-hander counterparts. I think an option could be to create (good) defensive skills that require a shield equipped. For example, "Shield Wall" - gives you a 50% increase to physical armor. Or perhaps add an ability related to Shields; like "Shield Mastery", with something like a 10% --> 15% --> 20% etc. scaling of increase to physical defense provided by shields.
Could also add in the all-important Shield Bash option, allowing you to either displace or stun an enemy.
