... What? Out of curiosity, and of course without revealing info on your identity and past employers, could you please provide a bit more info on the thought-train of these people? What kind of products/services did they make? Why would they choose that kind of strategy?
The problem with Dart, is right there in its feature sheet - advertised as something good; "compiles to JS". Have you ever worked with GWT? I did so years ago when it was much promising, 5 minute compile time for a small web-app on a core-duo... Whereas with js I could just alt-tab and hit F5. Or in the worst possible scenario I would to grap clear the cache first.
"Compiles to JS" means that testing in any browser other than Chrome is going to be a painful activity compares to simply writing js. If Chrome reaches 70-80% market share or if they manage to pull of something like in-browser Skyrim made with Dart, it might stand a change. Otherwise we 'll be here in 2 - 3 years saying "Remember Dart? Such a sad sad trainwreck...".
I absolutely love Sass. And I still don't understand why the W3C has not adopted many of those suggestions in the actual css spec. But then again, when was the last time the W3C did anything that mattered? It always was the open source community and the browser vendors pushing things forward.