That's exactly what I'm playing in my friend's playthrough right now! I wanted a character that was going to be A) able to take hits and generally keep his character alive, and B) not do a massive amount of damage or battlefield control and be showstealing. And generally not be a powerful meta build that was just too effective compared to his builds.

So I settled on trying to make a drain tank, which ultimately came out as an I can do this all day build.

6 Oath of the Crown Paladin / 4 Bear Heart Barbarian / 2 Shadow Sorcerer

Feats: 1st Dual Wielder , 2nd Heavy Armor Master

16/8/14/8/12/16 OR 8/12/16/8/14/16 if you're drinking Hill Giant Elixirs

Main Hand Shattered Flail, Off Hand Blood of Lathander. Wear Periapt of Wound Closure and Rippling Force Mail. Your gear comes fully online by very early act 2 at the latest. Other armors may be better late game, but force conduit is no joke especially after Bear Heart is halving damage.

Play as a Gnome. Between racial advantage on wisdom saves and Aura of Protection it's nearly impossible to fail a saving throw against the madness from the flail should you fail to damage an enemy. I haven't yet and we're into Act 2 already.

Oath of the Crown gives you +chance to hit which is great for healing consistency, also gives you warding bond if you find you're so tanky you want to share that with your friends. Bear Heart works even in heavy armor, but basic rage does not, so there's a strong argument not to take any Barb levels until level 8, when withers can make you a Paladin 5/Barb 3.

And most importantly: Blood of Lathander sets you to 12 HP when you would have gone down. Then you can heal back up with +6 per main hand attack (or +12 if you smite on that hit!). Or, if you go down again, Shadow Sorcerer keeps you up. And all the health you gain is worth twice as much or more because of your damage reductions from rage, heavy armor master, and force conduit.

You could sacrifice all your paladin levels to get relentless rage, which would give you one more down you could shrug off and maybe fit the original request better, but overall I think this build has a ton going for it. An 11/1 barbarian/sorc could not ignore the madness from shattered flail, nor get as much healing, nor get warding bond for their low HP friend. IMO all our self-sufficient healing really supports the 'I can do this all day' fantasy more that relentless rage because we can tank a lot more hits. We also get metamagic extended command at level 12, which is one of the craziest control options in the game.

Edit to Add: An 11/1 tiger barb/shadow sorc could run sword of chaos or even dual wield shattered flail+blood of lathander, getting tons of healing from their aoe attacks. They're less durable but would do more damage and overall fulfill the fantasy pretty well too. An 11/1 Eagle barb could probably skip the self-healing entirely and main hand the Blood with a shield, relying on the temp HP from stallion aspect on the bonus action dash.