Re: What about next year????
The entire Steelers D will be fine at every position next year with the exception of ILB and NT. One of those, if not both, is sure to be addressed in the first two rounds of the draft, depending on whether or not we take a guard first. In a worst case scenario, if we have nobody at NT, Hood and Mclendon could platoon the position (assuming neither is dominant enough to take over completely) with Heyward rotating in and out at DE. Outside of that, and Farrior's ILB slot (which I'm not too worried about), no other component of the defense is going to suffer a serious regression or need to be drastically improved.
Harrison, Timmons, Woodley, Keisel, Hood, Polamalu, Clark, Gay, and Ike are all fine right now, and will be for at least the next two years before any of them REALLY start to show any age. The "30" thing really only applies to running backs who are absolutely pounded every play, for pretty much every other position it's more like 35. Not to mention Worilds, Allen, Brown, Heyward all look like they could make major contributions if anybody at their positions actually did start to severely under-perform.
The reason we had trouble getting pressure was because both of our pass rushers were hurt all year. Even when they were playing they weren't 100%.