In Maya, you are suggested to generate characters by "Bind skin" (Skin bind / Smooth bind) with polygon mesh and hierarchy skeleton (Joint / HumanIK skeleton). It is fine to set characters in a T-pose without other rigging controllers.
Using FBX (version 2012) to export: Select preset "Autodesk Media & Entertainment", and enable "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 (use the Maya Human-IK preset for quick bone mapping), and adjust for posture alignment. Click "Convert" (enable "Geometry") and export the iAvatar file to the iClone Content Manager.
Go to"Actor" >> "Avatar". Find the character in the Custom folder you just exported from 3DXchange5.