I don't think he counts on 'hitting' and 'missing' as much as he stockpiles -options- in case one fails.
For example, Wynn was the first round pick to be used, Brown was going to be the backup plan (since Brown was acquired DURING the draft), and they were, I think, going to compete for spots.
We obviously notice the individual 'misses', and count him 'lucky' he had another player ready to step in, but I think that's the wrong way to look at it. I think he doesn't actually -care- if he hits or misses as much as he just stockpiles as many options as possible and then shifts through it to try and find gold. He may simply have a good option that we never know about because his first option 'hits' so well the other options don't come in play.
(Kinda like Garoppolo and Brady, in my view - Brady played much better much longer, so having Garoppolo ready to replace Brady never really materialized and they traded Garoppolo for -something-.)