WD Plague of Toads graphical bug

Hey, just played through with WD and i realised that Plague of Toads can jump around in the following area. http://i.imgur.com/I9ieS.jpg - It looks really weird when the toads are jumping up and down on an invisible floor.

I know this is a minor bug but it just didn't feel right, I know Blizzard like their games to be 100% so hopefully this is fixed.

Also this is my first bug report so let me know if you need any more information.

Thanks