For all that is wrong with flash as a platform, I have always found Actionscript 3 to be a far better structured and easy to work with language, compared to something like javascript, which has a very 'organic' structure.
I think in this case, and the comments seem to confirm, that it's an issue with the SOAP/XML encoder's handling of null values. That aside, AS3 doesn't bug me too much, my biggest issue with Flash/Flex was how it handled programmatic audio elements so differently from video/clip elements, that is/was annoying.
Of course since Adobe has all but abandoned the platform, it probably won't be much of an issue in the future... Kind of a shame, as Flex was actually pretty nice. If adobe was more open with the flash client as a platform, and focused on the tooling (where they make their money), it could have been integrated into browsers, and had a much better chance of sticking around.
There was a point where Adobe had a chance to evolve flash into a platform for creating HTML sites and applications (much like coffeescript, LESS, or any other intermediate might be). It certainly would have involved open sourcing large components of the platform, which they seemed to be against.
It's a real shame, since the closed source aspect of Flash really led to a brain drain within the community. Flash for many years was the superior platform for making complex web applications, but sadly, it did not have the community and brain trust that more open standards did, like HTML and javascript did. In the long run, this led to serious stagnation with the platform.
Also AS3 has strong static typing, a huge advantage, as we've just heard once again yesterday:
[...] the value of types is super super important. [...] Everything that is syntacticly legal, that the compiler will accept, will eventually wind up in your code base and that's why I think that static typing is so valuable because it cuts down on what can kinda make it pass down there. I'm only getting stronger in my stands on static typing, static analysis.[...] - John Carmack, qcon keynote 2013
I actually feel like AS3 could go further with static typing. Due to things like promotions with arithmetic operators, you lose some performance. I always felt it would be better to either force the user to explicitly cast between floating point operators and ints, and crash if they tried to do something with an int that would lead to a float.
What's the issue? CF makes writing web services stupid easy. Just add access="remote" to a CFC's function. Instantly introspected and performs all SOAP conversion for you.
Now, I'll admit, SOAP anything is crazy, but based on the age of the application, may have been the best option at the time.
I can't speak much to ColdFusion or WSDL though.