To find something so fundamental missing with no reasonable solution (and no information from the Dart team) is frustrating; it's not going to make selling Dart to my colleagues any easier.
Google has such a poor track record in language design, that when I was looking for a compile-to-JavaScript language I didn't even consider Dart.
http://blog.dantup.com/2014/05/web-development-sucks-and-its...
And while responding to comments, I read a little more about Dart and it started to look quite appealing. I spend too much of my day maintaining and debugging legacy JavaScript written years ago in sub-optimal ways.
However, it doesn't change that the complexity being used as an excuse is not being requested. There are many things people would want to do with their deserialisation, and nobody is asking the Dart Team to provide them all. What is really basic, however, is deserialising data into a flat PODO so that we can take advantage of code-completion and static analysis on our code; isolating the mapping problem to a single point.