Protection
“Nobody falls while I am still standing.”
Protection comes first because it came first. Her family spent three generations making the steel that stood between Lakeshire and the dark, and Harper grew up knowing that a blade exists for the people behind it. She wears the heaviest plate she can carry for the same reason. The armour is not for her. It is there so that whatever is swinging hits her instead.
In a group, that means she watches the healer as closely as the boss. She peels for the casters, plants herself between the adds and whoever is weakest, and saves Divine Shield and Lay on Hands for someone else's worst moment, never her own convenience.
In practice: peel for the healer, save Lay on Hands for a friend, and only bubble when it buys the group time.