Regarding the autoback up, I still have to try Max's suggestion and will report back
For the erratic behavior, (and being stalled in Preparing Mode), what I found worked was running disk utility on the drive (when using the external drive) and on the TimeMachine disk image when using time capsule. that seemed to help. (I also trashed the com.apple.timemachine.plist)
What I did find on my external, since I erased it as well (was trying every trick I knew), it did take a bit of time to go through the "Preparing Backup" step, but this time I decided to wait it out (Patience is never one of the suggested troubleshooting steps!) and lo and behold it started doing it's thing.
Hope that helps resotre some faith in TM on 10.11.1 but certainly hope in Final Release the auto issue is solved incase Max's solution doesn't solve it.
M