Rutger-Now even in chapter 4 there is use for this on him, namely when it comes to killing Eric. It allows him to take 2 shots from Eric without dying (which is otherwise impossible unless you not only get lucky with Rutger proccing 6 Def, but Eric has to be using his Javelin which will render Rutger to a WTD). This affords him a full turn to deal a decisive blow to Eric with his Killing Edge, whch in terms of bumrushing, could save us that turn, or otherwise make Rutger's job safer in bosskilling. Now with the more noticeable stuff in chapter 5, it lets him take 2 shots from iron axers without dying (they're not going to hit him anyways, but it still kills risk), 4HKOd by iron mercs, 3RKOd by 19 ATK Steel mercs, allows him to take the iron and steel nomads without dying (and he would be their most likely target), and the effects of the Robe remain as he levels so it can only help his long run. Even saves his long term if you choose to promote him early.