I hadn't seen much of one when I joined in, aside from surviving in the Clockworks in a world where the Swarm had taken over. The very first post in the RP has stuff like:
The Apocrea have become deities. A whole cult has begun following them, turning against the Spiral Order. The Swarm has overrun Haven, and countless knights are now infected. All survivors have fled to the Clockworks, with no sembelance of order. It is now your job to survive.
No Apocrea, no knights following the Apocrea (at least not many of them, I should say). Basically there is a situation at Haven, with Creos and the invitations, and right now my arc is basically prelude to going to Haven and trying to reclaim it I suppose. And then that leaves:
All survivors have fled to the Clockworks, with no sembelance of order. It is now your job to survive.
Which is what everyone was pretty much doing.
So what else really should be happening? At least according to the listed goals.
I think you've hit the nail on the head. The posts don't feel like they're being guided toward the story's goal. This is actually one of the more fundamental roles of a forum game host - to tie everyone's individual posts into the greater plot. Correcting the problem is theoretically simple: reel everything back into to story!
If this were a fanfiction, the writer would be responsible for everything - the beginning, middle, and end. The main advantage of telling stories in RP format is that you can outsource much of that writing to other writers, with the disadvantage that you lose some control over the story. To solve the problem, then, it's important that all the involved writers, especially the game host, keep in mind the greater plot when forming their story posts.
I also have some tips specific to the game host/master, Sawhero. As GM, there are several effective ways to direct the story. Ideally, you would be able to set up the world perfectly and all the players would know exactly what to do at any given moment. In practice, it rarely occurs, but I have seen it happen on some occasions. If you can pull it off, that's the best way to direct the story.
Alternatively, you could lead players by the hand and always be there to tell them what they can and cannot do. While this is a useful format for open-world games, it's very GM-intensive and requires constant attention on your part. I personally can't handle that very well, but other GMs can pull it off.
The method I prefer is to create a strong central character around whom the plot revolves and make that my main character. In that way, I can both participate in my own game and direct the story at will simultaneously. The downside is that if the game master ever god-mods, power-plays, or otherwise abuses his character's power, the game will crumble. It's vital that the game master be fair with his character if he wants to keep things flowing smoothly.
However, it's equally important that the game master's central character not be too underpowered. If your central character is too weak to drive the plot, then you can't drive the plot, and the storylines splinter. That's what we're observing in Outnumbered: the game master's central character is too weak to drive the plot. It may sound strange to say, but Sawhero needs to make a character that's critical to the plot if he intends to use this plot-driving method.