Golden Girl

Not when some people still seem to be wanting it to be just as fast as the Trial path

They've said it will be slower than the Trial path.

Basic design goals don't change in beta - the 15 Empyrean idea was to reach the goal of getting more than just BAF and Lambda run on a regular basis - based on player feedback, they changed it to giving more rewards for the other Trials - the goal was the same, it was only the method that was changed.
Dark Astoria is already done - the design goal is for a solo Incarnate path that's slower than the Trial path - that goal won't change - all we can do is affect the methods used by the devs to reach their goal, not the goal itself.
By the time any beta comes around, it's already far too late to make any changes to the basic ideas behind the new content - a good recent example would be the CoT revamp or the superpacks - we managed to get both of them tweaked, but the design goals behind them didn't change at all.
The basic design goal of Dark Astoria is already in place - the zone, story arcs, enemies and rewards have all been based around it, and that can't be changed - we'll be able to tweak the zone, story arcs, enemies and rewards with our feedback - but we won't be able to change the baisic idea behind the zone - a solo Incarnate path that's easier and slower than the Trials

The clones are easy because they have no personality or motivation - costumed villains have their own personalities and motivations, and they need to show them, otherwise they just become normal goons.
In the Protean example I mentioned, Vandal, Nosferatu and Requiem have their own personalities and motivations, so those would need to be written into the story arc - there needs to be a reason why they're there, and they need to express themselves, even if it's only with 1 or 2 text bubbles.
But because they'd have to be written into the story, that means they'd have to be there in the end fight, which wouldn't work if were are less than 4 heroes running the arc.

Because it takes longer to form leagues, and they have tougher challenges on them - the DA enemies are 50-54, and the Trial enemies are 54+ - solo content also doesn't requie the amount of co-ordination and teamwork that group content does, and because it's less complex and difficult, there's less chance of solo challenges being failable.
Leagues take longer to set up, require teamwork and co-ordination, fight the toughest enemies in the game, have the most complex mechanics - that's why they give the best and fastest rewards in the game.

Rogues have access to it

Ouroboros already being split between blue and red probably doesn't help either.

They'll be back soon

I think that there'll have to be random Incarnate salvage drops on the solo path to mirror the Trial path - it'll be much easier for the devs to balance the 2 paths it they're both using the same reward mechanics.
For example, right now, the Trials give 1-2 Empyreans at the end, plus up to 4 Astrals for completing certain in-Trial objectives, and a random salvage roll at the end, with some Trials having a guranteeed rare or very rare at the end - so one story arc could = 1 Trial, but with a longer completion time, fewer special objectives to reduce the amount of Astrals from it, and no guranatee of a rare or very rare at the end, as well as a slower drop rate for Threads from the enemies on the arc - and depending on how many arcs DA will have, and how long it'll take to complete each one, there could also be an Empyrean at the end of each arc.

If, say, somewhere like First Ward was an Incarnate zone, that'd mean players could earn 8-16 Astrals, 8 Empyreans and 8 random salvage rolls during one full play through of all 8 story arcs in the zone.

I22 also means that the Trial path reward progress will be faster, as there won't be the total drop off in rewards in between Trials like there is now - instead of going Trial/wait/Trial/wait/Trial, we'll now be able to go Trial/DA street sweep/Trial/Incarnate mission/Trial.

Too many Heroes there to stop your evil plans

I already said that the Rogue Isles were ok

The nurses are giving you a progress report on some of the injured people you recently saved from violent situations like muggings or kidnappings.

That can be difficult when team sizes can be between 1-8 - there could only be one "real" costumed villain for us to fight, and 1-7 "fillers", depending on the team size.
For example, when we fight Protean on Jenni Adiar's arc, the game adds "filler" 5th Column with him, based on the size of the team - having more or fewer of them with him doesn't really change the story, because it's all about fighting him.
But if there were costumed villains instead of the 5th Column, then they'd have to be very generic, and not have any impact on the story, as there's no guarantee they'd all always be there if the team wasn't a full 8.
It works fine on, say, the KTF, where we fight 5 AVs in the final room, because there's a minimum team size, so the game knows there'll always be a certain number of heroes in that battle, so the story can be written to include all 5 AVs - but that can't be done very easily for normal story arcs, because every story arc needs to be soloable, so the game can only ever calculate encounters from the idea that there might only be one hero doing the arc.
Like with the Protean fight, the game has to make it Protean plus x number of 5th Column because it has to balance it with there being 1-8 heroes - it can't make it, say, Protean, plus Vandal, Nosferatu and Requiem, because there's no guarnatee that there'll be at least 4 heroes on the team - which means it'd have to remove one or more of the named bosses if the team was smaller than 4, meaning that those named bosses couldn't be written into the story, just in case the team wasn't large enough to spawn them, which would totally remove the impact of going up against a group of individual costumed villains.
All normal story arc boss encounters are based around 1 named boss plus x number of goons vs 1 hero plus 1-7 friends, which gives total flexibility for team sizes, with zero impact on the story.

You could always play the story arcs and do the repeatable missions instead of just street sweeping

Listening to constructive criticism is totally ok - but totally negative criticism can be ignored.