I see it the other way. A top pass rush makes the secondary better. A top pass rush also creates turnovers. If QBs have all day, the don't tend too make too many mistakes, no matter how good the secondary is
QBs will not get all day though no matter what. An elite pass rush can stall a drive or two, but he will get time and he will get points. Meanwhile an elite secondary allows you to both take a teams best players out of contention, what is known as the BB special, and manufacture a pass rush by sending more guys knowing your elite secondary can cover.
You build an elite secondary, you buy a cheap run stuffing NT, and you just profit from knowing they will not score on you.