Kiwanuka does only have 6 sacks, but if you look at other DEs currently projected to go in the 1st round thats right in the mix. Pollack has 7.5 sacks, Spears only has 3 sacks, and Erasmus James has 7 sacks. You also have to look at the fact that Spears was considered a pretty high 1st round had he have come out last year, and James also plays with Hawthorne who is the 2nd best DT in this year's draft.
Also, as for Kiwanuka not dominating enough, have you watched him very much? He's got 41 tackles, 12TFL, 6 sacks, and 2 INTs including one that he ran back 32 yards for a touchdown. Thats pretty dominant considering that BC has a defensive squad starting quite a few true freshman.