Add one of these to the power leads as close to the ESC as you can:
http://cgi.ebay.com/2700uf-Low-ESR-c...QQcmdZViewItem
One is really all that's needed, plus be sure to observe the polarity when you solder it in place.
They are polarity sensitive.
This will help ESC temps alot. It makes it smoother on power delivery too.