My plan has been to finish decent drafts of all the chapters, sort of step back and look at the dissertation as a whole, and then revise each one. At the point I am at now, in my third year of ABD I can see that my first and second chapters are probably the weakest and the latter ones the strongest.
It looks to me as if you are exactly on track -- as a dissertation supervisor, I like to see each chapter draft when finished, but always reassure students that people learn how to write a scholarly work by chapter 3: inevitably the first two need a lot more revision than the rest, for the reasons you mention. Before you get too deeply into the revisions, however, I'd urge you to have the supervisor or one of the other readers who is familiar with the area in which you are working read the entire manuscript. I've heard from colleagues about students who went seriously off-track by revising unseen chapters badly. I never let my own students do that, and I also tell them to ASK all the other committee members if they want to see the full draft before you begin revisions.
Why? Not only for the advice and help you may get (which you can generally take or ignore, because by the end of the complete revision this will be
your project and not their's) but because this is the moment, leading up to the defense and the job search, that you want all your mentors to be quite familiar with your work, able to talk enthusiastically about it to people they see at conferences over the next year or so, and aware of opportunities you should know about.