Brooks sack numbers are a function of the defensive scheme. So the fact that he is getting 8-9 sacks is pretty darn good. As the Right side rusher, he is asked to contain more than the Left outside rusher. The premise is that Right handed QBs favor escaping right, so with left side pressure, the Right side rusher has to set a high rush and contain so the QB is forced to escape low and inside rather than rolling out free. Brooks does an OUTSTANDING job of playing his rushing assignment.
Note that you rarely see Brooks stunt inside like you seen Aldon and Smith do. That is because when a QB escapes left, he is far more likely to float back from the line of scrimmage because his throwing motion (arm to the inside of the formation) requires more space from defenders. And in general, QBs running left are moving slower do to this awkward throwing motion. Thus, the left DE stunt to the outside has more success containing and disrupting the throw.
On the occasions where Brooks is allowed to use and underneath rush move, he is devastating. In those cases, either the S or ILB is taking contain responsibility on the right side (often a Bowman highlight as he comes blazing in to pursue the QB!
Successful outside rushers are usually highly skilled with the technical side, hand placement, swims, leverage, hip sinks, etc. Pro tackles are usually so good, without the technical refinements, most college rushers are mediocre in the pros at best. That is why rookies are so quiet.
Aldon Smith is the exception, his long arms and surprising power (from a thin frame) allowed him to succeed even as he improved his technique during his rookie season. He should have been unstoppable last year, but he missed too much time in rehab. depressing.