Full, encrypted, point-in-time Mac OS X (including data) backup and restore employing Drobo as backup-storage device?
I run OS X server and use Time Machine to store things in an encrypted manner. I use a Promise R2 box for the actual storage instead of Drobo, and have not needed to use the AppleCare that I pay so that I get three years of Apple engineering support in case Time Machine acts up for me.

It just hasn't been an issue across the handful of clients that I've set up with similar setups. I used to lose a few backups a year when we were backing up to Time Capsule - but since using OS X server.app to handle the Time Machine - things are much better in a reliability standpoint.

Hopefully someone will have a good answer for Drobo since you have had bad experiences with Time Machine, but I wanted to chime in with what has worked well for the last 3 years. Of the 50 machines backing up over Time Machine, we're not seeing problems with Apple's encrypted backup solution.