By your own numbers, 65% of mutations are perfectly fine. To me, that is the definition of "fine more often than not." You know what you could do in Vegas with 65%? - I have a different view of those numbers: 70% going nowhere or worse. This is why Haldane raised the issue of his dilemma, as it is called. Evolution advances very slowly, as it is well known, so some species in a rapid change of nature might die out faster than they can adapt.