The Crimson Binome
Hero
It's counter-intuitive, but these two points actually work against each other. In a party, the barbarian's job is to be a large, salient threat, which can grab the attention of the enemies. You want them to attack you, instead of your allies, because you're better at taking a hit. (You also have a lot of free healing, every day, in the form of Hit Dice.)1) Rage apparently gives you resistance (half damage) to absolutely all physical attacks, is that right?
2) Unarmored Defence allows for a better AC than a fighter in heavy armor, possibly?
Having a high AC makes you less of a target. If the first three enemy attacks just bounce off of your rippling pecs, then they aren't going to keep attacking you, because it's futile. They're going to focus on hitting anyone that they can actually hit. You want a lower AC, because it makes you a better target; low enough to invite attacks, but not so low that you take unnecessary damage from an enemy that was going to attack you anyway. Something around 17 is probably ideal, for low-mid levels.