What is the simplest setup for rappelling that is fully redundant?
The most common system seems to be rappelling off of both strands of a rope passing through two rappel rings on separate anchors. While providing the option to recover the rope by pulling on one end, that setup still leaves the rope as a single point of failure.
Assuming the highest degree of redundancy is required, would it not be more safe to tie two figure-eight knots on two bights, connecting each to a separate anchor, and then rappelling off of those two strands? Thus if one of the anchors fail, or even if one part of the rope fails, the other strand is still fully intact.
Any specific reason this setup is not more common?