PodPress statistics is problematic for precisely what you've described.
blubrry statistics is a service not hosted on your blog, like Google Analytics is hosted else where. You can implement it in PodPress, or switch from PodPress to PowerPress.
I will say that if you have setup taxonomies with PodPress, converting to PowerPress will not be easy. We have developed migration tools, due to the complexity of taxonomies, we did not develop migration tools that go that deep into PodPress, simply for the fact that we haven't had someone come forward like yourself asking for the functionality (not too many folks use taxonomies for podcasting yet).
With that said, PowerPress has taxonomy and post type podcasting support built-in. It opens an array of possibilities, I highly recommend that if you have a sandbox to test with, install PowerPress and check it out!
If you are willing to share your database (the podcast posts and meta data), please contact me at cio [at] rawvoice.com. We can use that data to update our migration tools to import podpress taxonomies, which would be great!