I don't care how good your rush is, a modern day QB will eat a bad secondary alive. QB's have an internal clock, if you can't cover they will get rid of the ball long before the best of rushes get there.
Even the best pass rush in the league is going to consistently take 4-6 seconds to get home. You have to have people that can actually cover in the back end for that time.
I think we've seen bad (or perceived as bad) pass rushing for so long here that people think a good one will magically hit the QB after 2 seconds every play. You still have to cover, no matter how good your rush the passer.
Obviously, you'd rather be elite up front first though.