I actually think the Barbarians have some pretty beefy health statistics, easily topping 75 in Biesboch. I suppose they're moreso a brute than a tank, since they can target the backline, stun, and unleash a heavy hit. The only thing tank about them apart from their monster health pool is their ability to heal a lot of health but bleed in the process.
As for the basic classes, I'm thinking soldier is the closest you're getting to a tank class, with their ability to stack block in the early game.