What is ridiculous is your way of thinking that tanking is just taking blows to the face.
D&D is so rich system and gives so many tools to the players to build a character avoiding damage in different ways
A tank has to be able to take blows. That's the entire point of it.
What you are thinking about is (I assume) some kind of DEX-based "dodge" build with high AC from "other sources" that is much less likely to get hit to begin with - and/or utilizing magic/abilities to ignore or mitigate.
That's all fine and dandy - but none of that is tanking, unless you are able to take a few hits as well.
If you do such a build, and your "tank" takes a hit anyway (cause you can never FULLY prevent that, especially in low-mid level range) and then crumbles over because of low HP. Well, that's not much of a tank now, is it?
You need both, the lower chance of being hit to begin with and the capability of withstanding the hits that do come in.
Nobody is talking about the classic tower shield-high-CON combo, although that certainly is one of the most viable in terms of survivability.
And nobody demands 18-CON, either.
But some gimmicky dump-CON shit? While I'm mostly talking about PC gaming here, in a PnP scenario, that won't survive for long with me as a DM, cause my enemies act intelligently (well, if they do have intelligence).
I actually like making a female front-line fighter with 7 CON in D&D games (make CON a dump stat basically in modern parlance) , do it all the time, and have been since 80's... and they can tank totally fine.
That just tells me your DM sucks in providing challenge or willfully enables some gimmicky crap with unrealistic encounter design or you're talking about high level characters.
With high level characters, yeah, anything is possible. But we're talking about PC gaming here, where high level is what? 10-20% of the game?
That's not what this is about.
Most of the time (looking at BG, IWD, NWN or Pathfinder), you'll be strongly limited by what your low-ish-lvl character(s) can do, and a tank in that scenario will not be able to mitigate being hit all the time. It needs the HP.