I have a 76GB encrypted sparse bundle on the rMBP SSD drive. Mounting it by double clicking it in Finder was pretty much immediate in Yosemite.
With El Capitan a popup appears with "Verifying 'name of sparse bundle'" and a progress bar. The progress bar shows no progress and after fifteen minutes or so the popup disappears and the password entry dialog box appears. After the password has been entered the sparse bundle is finally mounted.
When I run the Disk Utility First Aid function on the mounted volume it finishes in a few seconds and reports no errors. Console does not seem to show any related messages during the mounting.
Is there any reason why this popup appears and is there a way to circumvent it? Fifteen minutes to mount a volume is just not practical.