To be honest, I've always felt like guys who have 1 great game have not proven anything. I know he probably had other good games, but his 4 sack game last year reminds me of Mario Williams, having a killer game once a year and disappearing the rest of the time (as far as sacks go that is).
I wouldn't swear that Barwin isn't going to turn it on again at some point, but, based on what I'm seeing, I'd bet money against him before I'd bet it on him.
Having said that, JJ Watt is getting all of the LB's sacks right now. You can't get LB sacks if your 3-4 DE is getting to the QB faster than the speed of light.