ALL Android Tabs are a pain in the BUTT when it comes to using External Hard Drives. Either they don't work, or work but stops after a while.
Take my Galaxy Tab 2 10.1--I can use my OTG Xs Drive with it provided I use the Back-up Battery pack that I have. Also the Tab has to be FULLY Charged. When in use the charge soon gos down and HD stops working. Same thing with the other one I got + battery pack. I think the only fool proof way is to try and find an OTG cable with double USB on it, so that one can plug in the Tabs own otg cable then incert the other in it and have it on Charge whilst using the HD. Manufacturers don't want us to use HD on their Tabs at this time because we will stop upgrading.ASUS Transformer is the way to go.