We recently made a pull request #6113 that was just merged. It should help the Blender FBX Amature export problem for Avatars. It looks like the FBX export doesn’t do the right thing w.r.t. joint pre-rotations, (aka Maya Joint Orient). It stores them in the wrong place on export. Anyhow, this change has the same effect as swapping the fbx “Pre Rotation” and “Lcl Rotation” which, @Menithal had tried in a previous FBX Madness thread.
These avatar’s still won’t quite work correctly with IK and hand controllers, due to the creation of an empty “Armature” root bone, but it’s a small step in the right direction. But we are working on that and should have a fix soon.
I’m a bit worried that the Blender FBX importer and exporter doesn’t handle the Joint Orient property well at all. But maybe it’s not that big of a deal, except when transferring stuff between Maya and Blender.
Anyhow, Let us know if you encounter any issues.