To say that he's not a "pass rush specialist" is simply to say that it's not ALL that he can do. If you watch his highlights, you'll see that he's VERY capable of rushing the passer. But he can also stop the run, strip the ball, set the edge, collapse pockets, and knock down passes. Do you really think a guy that has slightly more straight-line speed but sucks at the rest of those aspects is far more valuable than Okafor? If all we need is a guy to come in on 3rd down and run fast, then there are those all over the draft and there's no reason to spend a high pick on one. Personally, I think we need a player that can do it all if we are going to take them at 12. A speedster that just gets stood up on contact 9 out of 10 times is not going to make this team better IMO. Again, if he is being considered the "Terrell Suggs of this draft class", then honestly, we could do worse.
I get that, but there's one thing that we have to consider. We had a prime example of this in Ginn. All the speed in the World and no ability to actually make the catch. What good did it to him or us? Virtually none. You don't have to have 4.4 speed to stretch the field. Guys like Ginn may tire out defenders due to having to run down 40 yards a play, but sadly they get twice as tired walking back to the line of scrimmage because the ball hit the turf. The key is to actually get down the field and CATCH the ball. And I believe that Bailey's ability to adjust, create just enough separation, and snatch the ball out of the air, that is exactly why I think he's virtually perfect for that role. If you watch the videos, you can see how easily he catches balls out in front of him, over his head, and even behind him in traffic. It's extraordinary IMO.
One more thing to consider. Let's compare the expected 40 times of the group that you mentioned.
Bailey 4.45 to 4.48
Wheaton 4.40 to 4.45
Hopkins 4.52 to 4.56
Patterson 4.44 to 4.46
I took the high and the low estimate from several sites that I go to. You can see that not only are a few of the guys not faster than Bailey, but they are actually slower. Still though, someone like Hopkins may not have the foot speed, but he shows that his ability to be aggressive and get to the ball, can overcome his "lack of speed". And that's the exact same argument I'm making for Bailey. The only true "speedster" up there is Wheaton, but I'm still not sold on anyone that is truly successful in the PAC12...secondaries that give up 50 points a game only tend to skew the stat line and make potentially "average" players look like stars. I'm not saying that this is the case with Wheaton, but I just don't know if he's truly special outside of his foot speed. Just my opinion of course.