When you have a set up like this...

And you are engaged with the enemy to your left, clicking on the item will cause a very brief pause (~1 second), and then your charater will be on the other side of the enemy, where the item was (you will have picked it up.)
I have not tried this in any other configuration (me on top, enemy below, item below that, etc). I was able to do this consistantly in the bat cave.
Client version 0.0.19 (the latest milestone) for Linux on an x86_64, using the default server.