Definitely sounds like at least some Sonys have deep sleep issues. With properly implemented deep sleep there should be very little battery leak on android tablets. If it isn't with everybody there may be some app you have installed that is preventing deep sleep.
Yup there was an app that was draining it even in sleep. Its back to normal know but I'm not sure what app it was. I suspect 2 apps. Google chrome and the game Dead Trigger.