Here's my two cents. PP2 hasn't done much damage all year no matter who is out there. The chances of them scoring are low, and they are playing the top rated PK unit from the season that can turn the tables and put a shortie up on the board. Yeah yeah, I know their PK unit hasn't fit this billing this series, but they got close a couple of times to scoring a shortie in previous games and Laviolette isn't going to disrespect them because his PP1 unit happened to have success against their PK for 2 games (sidebar: Rangers 0/4 on PP last night). The approach appears to be to aggressively try to score with PP1, and then cautiously try to score with two defensemen on PP2. I think that's the right play against the Canes in close games or playing with the lead. There's no reason to risk letting a well below average PP2 unit give up a back breaking shortie. Perhaps if there was a combination that was more successful throughout the season, it'd be a little different.
I did take issue with the 3rd period PP strategy last night though. I don't think PP1 was near aggressive enough, and I think PP2 got out there too early to play the cautious approach. I'd rather use my best players to go for the throat, especially if they're producing, but that's just me. I also have 0 games coached and Laviolette has over 2000, so there's that.