Brain, I've never bought that. You still have to have good DBs, and if it were up to me, I'd take weaknesses at LB over weaknesses at DB any day. Chances are the weaknesses will be one-dimensional, and clear, and schemable. This is a lot safer than deciding all it takes is a pass rush, because unless it's an atypically great pass rush - dominant to the point of being historic - you'll still get exposed plenty. You can scheme against bad corners, and you'll see your share of that, but unless you use your front seven in a very dominant form - shutting down the run completely, shutting down the short pass completely and forcing a good deal of pressure on any long passes. Those three things are crucial to having a mediocre secondary, and a bad one includes prayer and adjusting an offensive philosophy to put more points on the board.
Linebackers can be more easily told where to go, how to react, where to set up, how to cover up their weaknesses. Corners can't be used as simply as crashing the B gap to cause disruption of the offensive scheme. Corners have to be on their stuff every down - if they slip, it's not an extra three yards in pursuit, it's an extra 25 and possibly six ponts.
I think a lot of people go with that theory because watching a pass rush is fun, and even the best corners get burned occasionally. In the end, you still have to have the absolute best of both possible to have a pass defense of a championship level.
Speed should help our situation somewhat. Range, mostly. The cover two is all about range, and our safeties and middle linebacker are very rangy. The outside spot, assuming Witherspoon is the nickel LB, should be rangy as well. That means, if nothing else, any gray area should overlap if necessary. We'll still probably get abused head on, intermediately, but in the short and long ranges we should see more help, and at the very least more people in position to make a good blow to the receiver.
