I dive with double redundancy on everything, and triple on some things, but that is my choice for the type of diving I do. Redundancy is always better than not, but an overkill with equipment isn’t necessary either. Today’s dive computers are very reliable, and if you use one for shallow diving without redundancy I don’t see a problem as long as you surface immediately if a failure occurs. And don’t forget that your buddy is also your back-up information source for depth and time.