11W was the full jetson TK1 board and it didn't even take PSU inefficiencies into account. Not to mention that the TK1 board runs different sort of memory that's not optimized for mobile. And all that was in extremely heavy gpgpu load, which no one does on mobile devices.
SoC power while gaming is around 4W for K1. The fact that it completely destroys every other SoC GPU wise in a really small case (mipad has the same form factor as the ipad mini retina) clearly shows you that it can't possibly have bad power draw. It would throttle in a couple of seconds if it did.
But here they are, beating apple, qualcomm and AMD SoCs with similar TDP, (and AMD and qualcomm ref tablets in bigger cases) by around 50% or more in GPU performance.
Just imagine what happens once they bolt some maxwell SMMs and their denver core to Erista.