When I import my overlay in Mocha, the track is perfect! Everything breaks down moving to AE. Not sure what I'm doing wrong.
If you are getting some tracking errors when you paste your tracking data from Mocha in AE then the errors are in the track inside Mocha. You'll have to clean up the track. Sometimes it's very hard to see these errors. I'd bet that if you looked at your track in Mocha carefully at 100% zoom factor you'd see the errors.
The most common issue is either your mocha and AE project are not the same frame rate, size or Pixel Aspect Ratio. First check these settings.
Another issue that will cause drift or misalignment is if your insert layer is not the same size as the AE comp. A good test is create a solid at the comp size and paste the track data to this to test.
I would recommend watching the mocha Fundamental video series to help: