I see that Arwen & Glorfindel have (almost) the same ability - "noro lin asfaloth" . I don't think it's a good idea so this is my proposal :
Since Arwen took Glorfindel's role in FOTR, i would keep this ability for Glorfindel and change Arwen's. Glorfindel is also a tank hero, so boost to his armour is very fitting.
I came along this quote from book: "A gift I will give you. For I am the daughter of Elrond. I shall not go with him now when he departs to the Havens; for mine is the choice of Luthien, and as she so I have chosen, both the sweet and the bitter. But in my stead you shall go, Ring-bearer, when the time comes, and if you then desire it. If your hurts grieve you still and the memory or your burden is heavy, then you may pass into the West, until all your wounds and weariness are healed. But wear this now in memory of Elfstone and Evenstar with whom your life has been woven!'And she took a white gem like a star that lay upon her breast hanging upon a silver chain, and she set the chain around Frodo's neck. 'When the memory of the fear and the darkness troubles you,' she said, 'this will bring you aid."
So i would like to build a passive spell around these Arwen's words. Heroes around her facing troubles and fear ( a.k.a loosing health points ) would look at arwen and get a "gift" of inspiration. They would get a boost to armour when below some % of their HP, and get knockback when near death. Exact numbers doesn't mather now.
What do you think?