On my character I can't see my offhand (except on the character select screen) when I have a wand equipped. In-game it's either wand out, or wand sheathed / by my side -- and that's it.
Other folks in my guild report the same issue. However, I started a thread on it on the official forums and one person says he/she can see his/her wand and offhand at the same time, and another person implied it should be possible (their response to the thread was "press z").
What's your experience with this ?