"Why is there hardly any evidence in the fossil record of the millions & millions of complex organism with failed mutations?"
Well, it seems that we do have such fossils. Almost all the fossils we have are of species that are now extinct, and almost all of them are evolutionary dead ends. Furthermore, they fit very well into the family trees that we build from existing species. Many of them are transitions that we would expect. These fossils include clear transitions between fish and amphibians, amphibians to reptiles, reptiles to mammals, dinosaurs to birds, primitive monkey to primitive ape, and primitive ape to human. I made a thread on the Archaeopteryx you may like to check out.
Another important point is that fossilization is extremely rare, and fossils are even rarer to find. It most often takes a quick burial followed by a quick solidification in order to prevent the decay of the bones. Most of the time, bones are simply consumed by microbes and other life.
We do have much more redundancy than we would expect. The evolution, given the fossils, seems step-wise rather than continuous. I think this is pretty well explaned with punctuated equilibrium, where the fossils tend to represent the stable majority population instead of the evolving minority. I bring that up because it seems to be a common objection, and I am not sure if that helps or not.