I thought I'd take the time to upload a Video showing you exactly where to position the Darkmoon Tiger against the Darkmoon arena so you can see how to get under the arena and able to loot the arena chest without any problems.
Achievement > Darkmoon Duelist
I'd Also like to thank WizardTrokair and credit him as he showed me the method of useing the Darkmoon Tiger to it's advantages. I took his Tips and Used them to my own theory.
Please take the time and enjoy. (Excuse the Music New Rig and Only Song on HDD)
(I posted this under Exploits and Exploration as I figured it's both? Please Enjoy.