Not sure what a sane, decoupled structuring for Backbone/Autobahn would look like, but thinking about such aspects upfront is very important.
FWIW, you can find a simple form example in 2 variants here:
The ExtJS code is using AutobahnExtJS, which provides specialized ExtJS data proxies for AutobahnJS.
The Knockout based code does not need additional stuff - it's also longer than the ExtJS variant in part because it is more feature rich. So you should not directly compare code length.
Personally, I find the Knockout+Autobahn approach quite nice: you have a clean layering: Autobahn real-time code only interacts with the view model, and the view model is data-bound to the views.
Disclosure: I am original author of AutobahnJS, AutobahnPython, AutobahnAndroid and work for Tavendo.