The state of REST interfaces as driven from anything other than an interactive browser isn't very good. HATEOAS is a nice principle, but it leads to interfaces that are very strongly people-oriented and it tends to lead to the burden of the user interface being put on the service developer (who is usually pretty busy making the service itself work).
WADL itself isn't too great; it doesn't really capture enough of the semantics of the service to make it possible to tool things up. Of course, this is a hard problem in general. WSDL rarely exposes enough information either, and that's had a lot more effort put into the problem (it's possible to attach enough information, but hardly anybody actually does so).
Yet it is telling that a colleague of mine has spent months working on a library that uses a REST interface to a service, and the WSDL-described interface to the same service[*] was tooled automatically to nearly the same quality in seconds; going the rest of the way was about a day of writing wrapping classes. My hunch (based on a limited sample size) is that you cannot get rid of all brittleness in a complex service because the semantics of the service will inevitably evolve over time, and that REST is better at driving interfaces for humans while SOAP is better for interface libraries (there's good WSDL/SOAP client tooling for almost all languages of note). Unless you've got the luxury of doing both, which one to focus on should depend on which set of clients you care about most.
I wouldn't put much effort into WADL, but if your REST framework will produce it for you (Apache CXF does this) then there's no particular reason to not provide it. Anyone who wants to tool off your code will want WSDL+SOAP.
[*] As the author of the service in question, I can say for sure that both interfaces supported the same operations — there was a common underlying abstract model — and in a “natural” style for both interface types. On the service side, it was definitely the case that some things were easier with REST and others with SOAP.