Is it normal for it to take hours to delete a Time Capsule "sparsebundle"
It is theoretically possible if the drive is near full that a delete operation may take a lot of time. You can try to delete the file via the command line, which bypasses the Finder and does it the Unix way. 

In any case there must be hard drive activity during the process. If the drive is not making any noise or light, then it’s not doing anything and that’s not good. But be patient.