Brown was FAR from the best rusher that year even before the draft. In fact, that year was full of fool's gold for rushers. Brown was fast and quick off the line, but couldn't change directions and wasn't explosive enough for his size. Maybin didn't have great COD as well, but was also SLOW for a rush end. Ayers had no explosion what-so-ever AND couldn't change directions quickly.
Even if you just look at the numbers, Orakpo had everything you need as far as the physical aspect for a rush end or OLB in the 3-4. He had size (263lb), speed (4.63s), straight line acceleration (1.56s), explosion (39.5in), and the best COD of any of the guys listed in that bunch with a 7.26s 3-cone drill. The next best, BTW, was 7.52 by Maybin for reference.
So this year if you want an OLB to rush the passer, look for a guy with some weight (240+ lb), speed (4.69s or better 40), initial quickness (1.60s 10yd or better), explosion (35+in vertical), and change-of-direction (7.30s 3-cone drill).
Oh and in case you were wondering, Matthews had it all. 240lbs, 4.58 40yd, 1.49 10yd, 35.5 vertical, and an AMAZING 6.90 3-cone time...better than many RBs...including Adrian Peterson (7.08 ).