In a system where +1 is as big a jump as it is in 5e? It should be plenty to have +3. That’s Legendary magic weapon territory.
Though that isnt where I am thinking about too much... i am concerned how much is +3 added to non-proficient activity Intimidate or Deception use for my Chosen one I have using in my example. I guess it does make her as able as someone with basic proficiency in say Heroic from the default rules. Which hmmmm .