I think you're missing something about tank design. It doesn't matter if you can survive the longest in the party, your enemies will simply wipe out your allies and then laugh as you hit them once for less damage then a single attack from any other martial class. You'll die last in a TPK, which isn't great.

See, barbarian is a great tank class. They resist the 3 most common damage types right off the bat. Then they get advantage on strength checks, so they can grapple to prevent enemies from moving easily. Then they can encourage enemies to strike them by using reckless attack, and their armor class is relatively low unless they build for it, encouraging attacks even more.

See, if you want to build a tank, surviving is just step 1. Step 2 is making sure you're actually preventing damage from reaching other party members, either by forcing enemy attention on you (via something like ancestral barbarian's hit-to-impose-disadvantage-on-other), preventing them from being able to damage others (your defender subclass is the only one who does this in any meaningful way), or reducing the damage they do to others (again ancestral barbarian's hit-to-impose, and also spirit shield at 6th level).

The best thing you can do with this class is grab a level of warlock to use eldritch blast. That scales with level, so at least you'll be doing 4d10 damage per turn at tier 4. Still, it just looks utterly boring to play.