JJ is what Cole did for the Pens and is needed. You need those guys who can take the beating of constant forechecking. Now obviously he isn't a top pair fodder, and as Emp put it, we can't really gauge this while injuries push him into a spot he should be in. He's not Letang who can handle top minutes and PK. Bigger guy, more energy spent. It is about managing the minutes.
Petts is a bit exposed due to having to be the next guy at LD up after Dumo went down. It's really hard to expect a D-core to be effective to the point where 2 of your best D-men are out. Everything kind of settles in once they are back. Since Dec. Petts has been playing a ton of minutes, and I don't see it as an issue and a learning curve being forced upon him. He'll be better for it, as will the team when they get healthy bodies back.
I also think Schultz could use the 3rd pairing support role until things click for him. He's had a tough few years in and out of the lineup. Constant partners changing.
Needless to say, I think they all could use some stability back.