I'm glad to hear the party is recovering and that their injuries are not extremely serious. The outcome could easily have been a lot worse.
As the incident illustrates, a belay redirection point has to be either the belay anchor itself (i.e. a multiple-point distributed anchor when gear is involved), or has to be constructed like a belay anchor, meaning at least two pieces and load-distributing rigging.
The same goes for a directional point that is way off to the side of the belay, as Jeff D. says. Such anchors absolutely cannot fail and so should never consist of a single piece, no matter how apparently bombproof it seems to be.
I've seen this principle violated repeatedly on Pink Laurel, where the leader traverses way left to the bolted anchor over Jackie. Using just a single piece for a directional at the top of the Pink Laurel corner is dangerously incompetent (no matter how purportedly experienced the leader is)---the failure of that piece would result in a horrendous pendulum, probably terminating in a ground fall, and there is plenty of opportunity to rig a multiple-point anchor there.
Leaders have choices about how much protection they use, but seconds are entirely dependent on what the leader chooses to do for them. This means that there is, or ought to be, a much higher standard for the protection of the second then there is for the leader.