I know this question was post way back but I just encountered this same problem on my old iPad2.
Was frustrated for hours with the same problem of unable to respond on a disabled iPad.
Finally had a Eureka moment - decided to use "Find My IPhone" app on my other device. Confirmed this is the iPad in question by first selecting "Actions" and then "Play Sound".
Once I confirmed this is the cursed iPad, I selected "Erase iPhone" and then just followed the rest of the steps to restore the iPad to factory setting. It's as good as new!
Now waiting for this once condemned iPad to backup from iCloud.
I believe this method is superior to the documented Restore from iTunes (connected to PC or MacBook) method; which by the way, didn't work for me whole afternoon.