Dude honestly we didn't draft cornerbacks high under Cowher either, the last one was Chad Scott and he was no shutdown corner. Lebeau's zone scheme does not place high value on shutdown corners so they usually draft corners after the first round.
Also taking CBs first round does not guarantee success, look at CIN they have drafted 5 first round DBs recently and their secondary isn't anything to behold. Simply throwing picks at a position is not how you do it right, that's how you end up being the old browns, snyder's redskins, millen's lions, etc. you get it. When you start strictly drafting for need, you become a bad team. The Steelers have always sought to draft BPA, now you can argue on whether or not the guys they took were the BPA, but to simply scream for one position if the value isn't there is ludicrous. The only CB worth taking at 15 this year would have been Fuller and he was gone, so you move to your next BPA.
You want to draft guys that you scouted and want and not simply what you need.