I'll take a stab for you on "1-11" for the Steelers. Keep in mind, this is solely my opinion. I'm sure others will share theirs:
1a. Polamalu- He changes how OCs must prepare for this defense on all levels.
1b. Harrison- He's not really far behind Troy in regard to being schemed for.
3. Aaron Smith- 2007 showed exactly how important Smith is, especially to the run defense.
4. Hampton- When healthy and motivated, as he is this year, you could make an argument for Hammy being #2 on the list most years.
5. Farrior- If Troy and Harrison are the heart and lungs of the D, then Farrior is the brain.
6. Clark- Not anywhere near as crazy as this might sound if you've been paying attention the past couple seasons. Clark is rarely out of position and has plus instincts. He allows Polamalu to get away with a LOT of freelancing. He's the 2nd most vital cog in their pass defense, as far as DBs go, because when he goes out it tends to fall apart quickly.
7. Taylor- Typically paired up against the other teams #1 WRs and typcially more than holds his own. If the guy could catch, he'd be a lot more recognizable.
8. Woodley- He wouldn't be near #8 on just about any other defense. Really came on this season. I liked him as a player at Michigan, but was afraid his best pro position may be with his hand on the ground(I'm still not sure it wouldn't be, as scary as that sounds). He's done far better in space, so far, than I thought he would by this point.
9. McFadden- Was having a great season before his injury. He has been worked back into the starting lineup slowly, but seems to be back to close to where he was at least.
10. Foote- Steady, but unspectacular. Can be had, but he's pretty much seen it all by now. Makes up for lack of athleticism by reading plays well. Plus, he's got the best H.S. team name/mascot ever.
11. Kiesel- Down year for him, due mostly to injuries, but he'd probably be last in line on this team in his best year anyway. Was billed as a guy who could rush from the 3-4 DE spot when they were developing him, but has only really been good for that one year. Still a bit of a liability vs. the run, although he has improved there a tad over the past couple years. Injuries are his biggest issue now, it seems.
Gun to my head, I'd actually put Timmons at #11, but since Kiesel technically starts(when he's healthy) I'll give it to him. Timmons has made far more plays in his limited time this year than Kiesel has, that's for sure.
Significant backups:
The aforementioned Timmons- They work him in at all 4 LB spots some games, but primarily sub him for Larry Foote. Great in coverage and emerging as a blitzer.
Townsend- Instincts are still good, though the athleticism is starting to erode some. Still capable of starting, and has done so when McFadden was injured and performed as good as could have been expected.
Hoke- Can still penetrate when called upon if Hampton needs a rest.
Gay- May actually be the team's best hands at DB.
Eason/Kirshcke- Neither guy has really been that great for the Steelers....until this year. Both are probably better at stopping the run than Kiesel is, so they become "significant" for no other reason than Kiesel has been banged up a lot this season so they've had a lot of reps and were fairly productive with them.
In my mind, the Achilles Heel of the Steelers defense is probably overall depth. The starters, and initial backups for most units, are good-to-excellent. Outside of LB though, none of the other units are THAT deep. Most specifically safety. BOTH starters are so important to this defense already, but it's compounded when you only have Tyrone Carter and Anthony friggin' Smith behind them. Carter can make a play here and there, but Smith is basically bread sitting on the bench waiting to be toasted by being inserted into the starting lineup. If either Polamalu or Clark(especially Clark) were to miss significant time it really changes the whole complexion of that pass defense.