Dual bladder does have it's own draw backs, the main one being that its another thing to check, service, etc and make sure it's working. I doubt most people really check the second bladder until they need it. Then there's the extra hose routing, and clutter associated with it.
So how is a bladder going to go wrong? Worst case, it could split because it gets over pressured. When's that likely to happen? When you jump off the boat. So make sure you give your over pressure valves a look every so often, and try not to inflate your bladder so it's ready to burst when you jump in. What else? Leaks, either from valves or just a hole. Well in this case, it's annoying, and you should probably call the dive, but it's not going to stop you getting out safely. It just might mean that you need to keep the air in one part of the bladder, or you have to top it up more often.
So for me, the key is not being massively negative at any point, which you shouldn't be anyway. That way, even if you lose it completely you're not going to sink like a stone. And realise that wing failures happen at the start of a dive, because of jumping in, or because you haven't checked it can hold pressure, so you should never be too far from help. Once on a dive, I don't know how you'd put a hole in a wing.