TI 2013 much slower than TI 2010

I recently upgraded from TI 2010 running under W7 to TI 2013 running under W8. It is significantly slower doing a full image of drive C to an external USB drive. Nothing else has changed. The amount of data being backed up is about the same. It's not doing sector by sector.

Also the estimate of time remaining is way off. It starts out showing an estimated time of 1 hour 40 minutes. The actual backup time is usually twice that long. So the estimate is useless.

Edit: I noticed that under performance options the default backup priority is Low. I'm setting it to Normal to see if that helps next time.