In Blender, you are suggested to generate characters by adding "Armature" with skinned mesh and hierarchy bone structure. It is fine to set character in a T-pose without other rigging controllers.
Using default setting to export:
Highlight class Armature & Mesh, and enable "include Animation" if animation is embedded.
Import the FBX file and convert it to a "Non-standard character". For characterization, rotate bones into a T-pose, map at least 15 bones, and adjust for posture alignment. Click "Convert" and export the iAvatar file (enable "Geometry") to the iClone Content Manager.
Go to "Actor" >>" Avatar". Find the character in the Custom folder you just exported from 3DXchange5.