The problem with making resilience "too" useful is that everyone would run 100 resiliance. As it is now it usually doesn't affect TTK (at least not on most weapons, but on low impact / high RoF it probably does) - it merely alters how many of the total shots that needs to be headshots in order to reach optimal TTK. I think this is fine for PVP - too much of a difference and it would become a must to max it out. I would rather have it that they added a secondary trait to resilience - what if higher resilience also reduced how much you flinch while being shot? Not much, but just enough to make it worth it. This would make the stat attractive without making it a "must".