If we're going to throw in a class feature to the fighter side, might we throw in one from the barbarian side? I mean, obviously everyone knows about bear totem at 3, but the temp hp that can come every turn from battlerager/storm herald are deceptively useful (even if they're not attached to amazing subclasses) at reducing damage taken throughout a combat. Ancestral Guardian can use spirit shield on themselves (crawford). All these features are also useful against critical hits.
Also let's not forget Relentless rage. Being able to stay up 1-4 hits longer then expected every short rest goes a long way when all the hits you're taking are big ones. Even if it just means the enemy doesn't down you on the first hit and then cause you to fail 4 death saving throws with their other 2 attacks.