Was there some compelling reason he has to rush through all this? It was annoying during Hivebent but he at least had a reason. Now he's doing it with things that are actually plot relevant (not just backstory) and it's kind of draining a lot of tension and emotional impact from these scenes.
He's answered this over the last couple weeks on the
Formspring account. He had a hardware failure, a convention, and a software failure, all in the leadup to Rose and Jack's fight, about which he said:
This was originally going to be a Flash project, but I cancelled it.
Everything happening now, and over the next bunch of pages, would have taken place in a pretty energetic, and much more sophisticated than usual strife animation. Kind of like "strife version 2", for the second disc. I planned this idea months ago, not really thinking much of the effort and time it would eventually require to complete. This is what I usually do, blithely make such ambitious plans, pay the price later, but fight through it with a major grind and honor the original vision.
This was a little different though. Not only was this meant to be a much more elaborate type of animation by my own stakes-raising declaration, with more frames-intensive visuals like a typical 2D fighter, but on top of that, the rate of output had been slowing, and the story flow was already kind of logjamming.
So I had to make a decision. I could either apply what I now estimate would have been two or three solid weeks of serious effort to make this one pretty cool animation, and watch several 100K people sink into a state of despair over the prolonged suspension in content only to have the story advance not particularly far through a totally radical battle scene, or I could scrap the whole plan and figure something else out. The latter is what you're seeing.
He goes on to explain that "practical considerations" trumping his original ambitions have played a large role in shaping the narrative so far, and in fact subverting expectations to play with the way the story's being told is a big part of what enables him to continue making Homestuck in the first place. Doc Scratch stepping in to narrate the last part of this chapter is a way for him to quash any expectations anybody may have about Flash showing up before the end of act, and to keep him from overcommitting to such distractions from the core narrative, since Flash content has generally had the effect of stretching out the story and complicating its production and sort of forced him into exploring more and more ancillary content to spread out the workload into manageable chunks.
The story's getting chopped up, dialed back, and slowed down as a matter of necessity, basically. Expect things to proceed like this for a while, and then the "usual awesomeness" should recommence at the End of Act.