I chose the term "Two-Faced" because Peter DeBoer is like a Batman villian. Like a Batman villian, he's someone who's very good at his job- except instead of commiting crimes, he's a very good coach. However, like a Batman villain, he's got his problems often which will cost him dearly- Bane is a drug addict, Two-Face can't make decisions, Killer Croc is an idiot and the Joker is insane. With over 100 games under his belt as the Devils coach, we've seen Peter DeBoer at his best and Peter DeBoer at his worst. Here's a look at what he does the best (and the worst)
The Good: Has an Excellent Puck Possession System
Since DeBoer has taken over, the Devils have been a very good puck possession team. While it took a while to adjust to the system, it was highly effective when it was finally in place. The Devils were one of the better fenwick teams in the 2011-12 season and were an excellent Fenwick team in the playoffs. The Devils continue to be a good fenwick team, as they're currently one of the better fenwick teams as of now. He's a bit conservative with a 1 goal lead this season, but other than that his system is very effective.
The Bad: Poor Lineup Management
There's a saying- "if it ain't broke, then don't fix it". Unfortunately for Peter DeBoer, he tends to try fixing things way too often. Devils struggling for offense? Put Steve Bernier on a line with Adam Henrique and Patrik Elias. The "John MacLean line shuffler" as I like to call it comes out quite often. It's usually not very effective at times, simply because some players won't work nearly as effectively with others. Stephen Gionta has his strengths, but if Ilya Kovalchuk can't score, he's not the solution. Not only that, but he often tinkers with stuff that's working. Patrik Elias is the guy you'd want out against the other team's top line, yet somehow the 4th line is out against them.
On the other hand, he can sometimes rely on players too much. While you can't complain about Ilya Kovalchuk getting lots of minutes, you can wonder why Peter DeBoer was willing to give so many minutes to Bryce Salvador, who's not even the 3rd best defenseman on the Devils and hasn't been a very effective player. He's willing to scratch Adam Larsson and Mark Fayne for making simple mistakes, yet he's unable to bench Marek Zidlicky after he makes several egregious mistakes. He's willing to bench Stefan Matteau so that literal waste of space Cam Janssen can play one game (and do nothing other than give a player a Macho Man Randy Savage style elbow). He rode Johan Hedberg and his piss-poor goaltending for 10 games only to lose 8 out of those 10 games. Heck, he played Eric "worst player in the NHL" Boulton for 51 games last season.
When he's not micromanaging the team to hell, he's effective. When he is, he's terrible.
The Good: Gets the Most Out of His Players
While he hasn't been very good at managing certain players, he's been very effective at getting the most out of his players. David Clarkson's the prime example of this- he went from an under-utilized (and unlucky) player under Lemaire/MacLame to a useful player who can score 25-30 goals a season simply by giving him more ice time. Steve Bernier, Stephen Gionta and Ryan Carter on their own are players who are either niche players that are at best bottom 6 forwards, yet he's managed to get the most out of those three. Marek Zidlicky went from a Malcontent in Minnesota to an effective offensive defenseman who's pushing play forward (10.81 on-ice Corsi).
The Bad: Not Very Good at Managing Young Players
While DeBoer has been effective at getting players to be very effective, he's not very good at managing young players. Adam Larsson, despite being very good at times, is often benched so that the less effective Henrik Tallinder or Peter Harrold (who we can all see why he's a career AHLer- he's not very good) could play. The same goes for Mark Fayne, who's often benched for minimal mistakes, while Captain Pylon and Marek Zidlicky could literally make the blunder of the century and still play 22 minutes.
As for the forwards, he's been a bit better in that regard. He's managed Stefan Matteau effectively. He put Andrei Loktionov and Adam Henrique in positions where they should be at their most effective. However, he's had some moments of mis-management. Jacob Josefson couldn't really do much playing 8 minutes a game with Krys Barch, so he got demoted because he couldn't make an awful player effective. Bobby Butler did play poorly, but he couldn't do much with mediocre linemates. Of course- some of his decisions are defensible. Stuff like benching Fayne and Larsson are absolutely idiotic and he deserves to be criticized for those moves.
The Good: Can Find Ways to Mask The Team's Weaknesses
Peter DeBoer's Devils haven't been a team that's been effective at generating shots- while they usually outshoot their opponents, it's more because they're able to prevent shots- one of the best teams in the league in that regard. This is why the Devils are a good possession team, but they're not a dominant one because they aren't outshooting their opponents by a lot. Of course, the low totals can be attributed to the Devils scorer under-counting shot totals, but even if you do adjust it (by adding 0.5-1 S/G and SA/G to the totals), they're still not very good at getting pucks on goal.
The Unfortunate: Percentages
One thing that hasn't helped him in his tenure as head coach- poor percentages. The Devils save% last season in the regular season last year was rather poor due to Martin Brodeur's poor early season play with his injury. This year, the Devils sv% was pretty poor simply because Hedberg was awful. This year the Devils can't score because they're shooting poorly at even strength. The PK and power play aren't DeBoer's problem (rather Dave Barr and Matt Shaw's), so you can't blame him for their shortcomings
Conclusion: DeBoer Brings a Lot More Good To The Table Than Bad
Simply put, DeBoer brings a lot more good to the table than bad. While he can be a bad coach at times (playing Krys Barch in the 3rd period while down a goal, questionable roster decisions), it's very easy to defend him (the team's awful luck) and he brings a lot more good than bad. The Devils did do the right thing by not hitting the panic button and firing him- there are very few coaches available that are as good as DeBoer. If hypothetically he did get fired, he wouldn't be in the unemployment line for very long.