For me, neither the line 323 edit nor the Spotlight exclusions fixed it. So I tracked down the issues in
symbolicatecrash and published a patched version on github. Just replace /usr/local/bin/symbolicatecrash and your iOS crash reports will start symbolicating again.
This patch may not work for Mac apps, as it makes assumptions about the structure of the .xcarchive directory which don't appear to hold for desktop apps.
Edit: you may still have problems if Spotlight hasn't indexed your archives. You can get force an index by running the following in a terminal:
More info on troubleshooting here.