I was having all sorts of issues with my TF300T after the Jelly Bean 4.2 update: unresponsive touch screen, excessive battery drain, spontaneous shutdown, etc. I have tried the factory reset multiple times, and the tablet would always seem better for a few days / weeks after the reset, but would eventually start to freeze up, reset, etc. I contacted Asus and was told it was either a battery issue, a motherboard issue, or both and that I'd need to send it in for repairs.
Not wanting to spend as much on repairs as I initially spent on the tablet, I decided to keep experimenting with settings and found that reverting to the Jelly Bean 4.1 launcher [Settings -> Launcher] resolved all the issues I had been experiencing. I definitely preferred the 4.2 launcher, but I'll live with the 4.1 launcher if it means that my tablet actually works.
I hope this helps someone else out there - it drove me crazy for months!