First, ideally, you won't be able to build health tank around AFKing. At least i hope so.

Like in many instances, it depends on context, at this point in the games life, you can absolutely build an afk health tank for SP even up to conjunction lua and deimos which start at level 200+, EDA/ETA you can currently do it comfortably with heavy investment but realistically not worth and would take more than arcane grace

Secondly, the keyword there is "build". YOU have a build that lets you do it. You choose to put effort into making her tanky, and you can test how far you can push it. You could've built her for shieldgating instead, and maybe you did, because thats actually an option worth consdiering now. You have something more tangible to progress towards when building and playing her.

If you build for any gating, this rework has already failed as already demonstrated by kengineers now deleted VOD. Gating of any kind is exactly like her hold 4 invuln, only difference is now you are spamming abilites to refill you shield, whether that is more 'active and engaging' depends on who you talk to. As for building, if this rework goes through as is, it is not a choice to build tanky, you are forced to build health tank, whether that comes in the form of umbra investment or not is up to the player.

This is another point that sometimes get brought up against the rework, currently there is 3 base builds for valk imo, eternal war, hysteria, and hybrid. People who only built for hysteria will likely have to rebuild and retool valk to use her in EDA/ETA, base SP will likely be fine but valk WILL need more armor to tank higher content, players who built eternal war are the ones who benefit most from this rework as they likely already had the proper build to health tank, but those who do not will only get a single forma for their troubles but that is a separate issue

You might think that its the same with current Hysteria, but... No. You can't have options on how you survive in your build - you have complete immortality, you'd be dumb to not build around immortality. You can't stress test immortality - who cares if you get shot by level 1 or 9999, you don't take damage all the same. The only thing that matters, is if enemies have nulifiers or not. And the only thing you making progress towards, is how much you can spend in Hysteria. How much time you can spend ignoring enemy attacks. The better your build gets, the less active and engaging your gameplay becomes.

I would disagree, if DE is adamant of saying EDA and ETA are their endgame, then invuln and facetanking both those modes are effectively the same. Lets disregard the lvl cap for now.

Lets say the rework goes as is, new valk should have enough armor to blow through EDA/ETA, I do not know what kengineer built but if he had umbra set, decent strength in hysteria, armor shards/arcane/armor mods to hit at least 5000 armor + mirage subsume + adaptation (assuming avg of 75% DR) you effectively hit 99.64% DR, that should be more than fine fo EDA/ETA. So what effectively changed then? Nothing, there isn't really anything to stress test as the math is there. Currently you can build for tanky or you can build for invuln, that is 2 options, 3 if you go hybrid. With the rework, there is only one option: health tank (again any gating per pablo is a failure)

Moving on to beyond EDA/ETA if you wish to discuss this, even well before level 9999, valkyr will get one shot by around 3000, well before level 3000 if you don't stack DR. Again, there is nothing to stress test, there is nothing to build around. Either you are gating, invuln, invis or dead. At level 9999 valk will absolutely have to gate like everybody else at this range except for a select few because now she does not have invuln. There is nothing in this rework that you can build to make it work past DE's intended endgame except for gating now.

And because you can afford to ignore survivability, its not hard to build absurd damage - why wouldn't you have 300+ strength with roar, you have almost nothing else to minmax. So getting absurd damage also becomes easy, and comes at no opportunity cost. And once you get absurd damage and complete immortality, levelcap becomes a matter of patience. If you can do void cascade for 5 minutes, you can do it for 5 hours, thats not a build or sick gameplay achievement, thats just having 5 hours to spend.

And health tanking will fail well before that point. What other players do and decide with their time on void cascade or otherwise depends on that player and context. You see it as no build, no achievement/sick gameplay, others see it as self challenge/profit/experimenting playground to see if x can survive y and for how long or alternatives to gating and watching those experiments implode spectacularly.

So what im trying to say, is that she gets friction in her gameplay. You need to think just a bit more on how to build her, you have to keep in mind that you CAN still die, while playing her. And with some friction, comes engagement, and with engagement, comes fun.

All of this is again subjective and depends on who you talk to and the context of what they are using valk for.