I think shield arts must have "taunt" or something equivalent, its kinda obvious, i don't blame you for not assume that.
btw, the wand she have replaces a healer, it makes simple healing as good as advanced healing with a super low mana cost, so it's much better that a party member that only specialize in healing, as said on the chapter, she have an immense amount of mana, hp and sp, its possible that she can do more work that 2~4 healers, besides tanking. It is super efficient.
@Wilhelm_Stenvall