This is not technically an integration but this seemed like the best place to put it. Over my career the absolute best project outliner and brainstorm program I use is Project Kickstart. I know it is a little pricey but I constructed hundreds of project outlines with this program because it acts as a brainstorming program like none other that I have seen. It is not a competitor of Asana but rather a way to brainstorm the construction of your project. With unlimited ability to re-arrange, indent etc you will be able to layout a hierarchy that matches Asana which is where you should end up. I know the owner from my many years of use. I am going to talk to him about creating a CSV output for the eventual template import I suspect that Asana will have. @Bastien_Siebman you should try the trial as I suspect you could really expedite in depth templates. Here is the web address http://www.projectkickstart.com/. For those of your that are heavy into project construction and executable tasks it is well worth it.
Would love to hear if there was an update on this