Well, what HAPPENED to Zoe?
So far, we have had a diffusion of the eternal-pain scenario by Rammer revealed to Riff he was lying.
There are a number of reasons that Zoe couldn't be Harbinger:
In Sluggy Prime Schlock needed Oasis to compleate "the triangle", which suggests Oasis/Kusari/Harbinger was neccesarry for the rise of 4U City.
And we know that dimensions Zoe died and was buried in another dimension.
Also, DoR Schlock "felt sorry" for Zoe, I don't think his first option when she returned would be to make her into a bio-construct when he had full control of the city already.
The way the characters speak about Zoe: "Visit her".
She clearly isn't up and about, why can't Riff meet her at work otherwise?
That could be visiting a gravesite, but everyone seem far to happy, I would think the suggestions to visit would be made more respectfully with a gravestone.
We know that she have been tortured by the burn pains, but also that that isn't the case any more.
Best guess is something happened to her while being fixed.
Maybe she is stuck in a continuus reboot, being unable to remember stuff from day to day.
-That would count as a psycological condition, so a psycological condition is the guess I will go for regarding her fate.
She could also be time-frozen like Aylee once was, but I don't see why that would happen.
Also long-term spec: Someone will go on a journey into timeless space in order to "fix it" = Oceans Unmoving 3