I have to disagree Bob, I think he's fast enough to rush from WOLB. Speed is only one part of the equation, heck James Harrison ran a 4.85 at the combine. It's a combination of power, quickness, and closing speed all of which Mario has in bundles.
Demarcus Ware's 2010 stats earned 1 Pass Defensed, and 15.5 Sacks. That should speak to how often he rushed the passer vs. played in coverage. The difference between Mario as 4-3 DE and 3-4 WOLB is a bout 1 step to the outer corner and picking his hands up on run plays.
Here's an article that talks about his success standing up...and note this is without any instruction from a 3-4 OLB coach:
Link
I think Keith is talking about getting some internal push from the NT which I agree with. Any internal pressure makes your outside rushers more successful, due to the QB having to reset his feet, or take an extra step back into the outer curl of the outside rushers. This works in the 3-4 or the 4-3.
I'm hoping we get to see some more A-gap blitzing from Brian Cushing in 1st/2nd down 3-4, and some interior rush from Watt and Smith in the nickel.