My current character is a tiefling barb with infernal constitution and a ring of necrotic resist. He's got resist to poison, cold, fire, and necrotic at all times. It's a huge a factor in his durability; resist to b, p, and s is good, but elemental damage becomes way too common outside of t1 for basic rage to be barb's only method of defense.
Fundamental problem of martials, in a nutshell. They're only allowed to do a handful of things, so they necessarily step on each other's toes while simultaneously being constricted on growth.
Honestly, fighter, monk, and barb probably shouldn't be different classes. Barb and monk are representations of two common warrior tropes...fighter is "everything that isn't barb or monk." It's pretty silly.