Treantmonk's Tank: Ancestral Guardian / Echo Knight / War Wizard

[Merudo]

If so that sounds like a terrible use of Ancestral Protectors/Rage. You should use it to protect other PCs from the biggest bad guys, particularly via granting resistance (disadvantage helps but is not enough), but the echo will pop due to almost any hit from anybody and then you have to summon a new one, which gives away your position and makes the real barb a priority target for at least one round (until he can swap places with his next bonus action).

Protecting the echo = futile.
Using the echo as bait and protecting PCs = decent.

I'm not sure what it's actually designed to do

Even with the hype train, a better name for it would be "the Work of an Enemy Stand".

Treantmonk describes the ideal scenario for his "Guardian" build at 29:50 of his video.

The Ancestral Barbarian 6 / Echo Knight 3 recklessly attacks the big bad monster with his echo before retreating behind the party. The big bad monster then has to move around the whole party taking multiple OAs (including one from the echo), or attacks the party at disadvantage and for half the damage.

Of course, this "tank" build falls apart the minute you are not facing a single big bad monster, or the big bad monster is not relying on melee attack rolls to do damage...

I appreciate the JoJo reference btw.