For example, a defensive brother using a shield, redundant against orc warrior and young orc does a good job at cleaving shield too. Good against arrow? Nay, those goblins will snipe your archer to death and won’t bother with him. Protect your archer against arrow? Plenty of time my archer die directly behide a shield-wall, guessing there no extra bonus to protect your archer except for block penalty. So why bother with shield perks? Maybe someone can prove me wrong.
If a lot of your company have been taken to tier 2 of the utility tree, so that they can wear heavy armour and carry heavy shields and form lots of shieldwalls and use Bags&Belts + Quick-Handedness to instantly replace a broken shield or (depending on the enemy faced) swap a kite for a heater, then the shield-based tier 1 defence perks suddenly seem worthwhile (especially Deflect against orcs). By that point, some of them will even be capable of carrying around one of those massive, heavy, semi-indestructible orcish shields. Sometimes, you can loot special rare orcish shields that have even more durability and/or offer more defence (with potentially greater or lesser fatigue). Combine that with Deflect and the shield is almost indestructible and would zap all the energy of any gang of orcs that did smash it (and you’d still have one or two durable back-ups).