Just for the record, the best character to "soak up damage in melee" is of course Wildheart Barbarian 7 with Bear Heart and Stallion Animal Aspect / Thief 5.

Wildheart 3 gives you Bestial Heart; Bear gives you resistance against every damage type except psychic during the Rage.

Wildheart 6 gives you Animal Aspect; Stallion gives you double Barbarian level temporary hitpoints whenever you Dash.

Rogue 2 gives you Dash as Bonus Action

Thief 3 gives you a second Bonus Action per round

Rogue 5 gives you Uncanny Dodge, allowing you to half damage taken once per round, using your Reaction. This actually stacks with Resistance.

Barbarian 7 gives you Feral Instinct; a slightly weaker version of Alert.

By the way Stallion doesnt care if you actually move, only that you used a Dash action. So you can just Dash with your Rogue once per round as one of your two Bonus Actions and refresh your temporary hitpoints, and possibly use the other Bonus Action through Thief 3 to consume a healing potion.

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On top of that, you can have a Cleric to halven the damage even further with the level 2 spell Warding Bond. This spell is available through a pair of Rings in Act 2, too, so you can have an Abjuration Wizard as the one who shares the damage (and, in case of Abjurer, mitigate it away into nothing).

This AGAIN stacks with the other two effects, so now your Barbarian only receives 1/8th of the damage, which then hit the temporary hitpoints first.

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If that still isnt enough, you can build a Lore Bard 8 / Thief 3 / Life Cleric 1 who picks Warden of Vitality as their Magical Secret. Warden of Vitality allows for 10 rounds to heal as a Bonus Action, and Thief 3 allows to have two Bonus Actions per round, and Life Cleric boosts your heals further, nevermind all the extra items you can use to boost healing even early on. So this character can heal 2d6 hitpoints twice per round, plus all the bonuses they can apply on top.

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The best tanking is of course to give your opponents this convenient Status: Dead. They all dont do too much against any of your characters after they received that Status.

So the best tanking is to go first and have lots of damage for single targets, and control for larger groups of lesser opponents.