It sounds like the Devils are done in free agency, so here's a quick an easy take.
The Devils biggest problems over the past 3 or so years have easily been poor goaltending, generally spotty team defense and being physically bullied.
Fitzgerald and co. identified this and addressed all three.
Markstrom is not prime-era Hasek, but he's still a top 15 goaltender in the league and the best netminder the Devils have had since Schneider.
Pesce is a legit shut-down stud at RD and a perfect pairing for Luke Hughes. Dillon is a physical beast and near-shut-down-stud at LD and a perfect pairing for Nemec. They are, respectively, the Devils best pure defensive-defenseman and most effectively physical defenseman in several seasons.
Cotter is a very physical and athletic bottom 6 LW who is a better skater and better defensively than Holtz, whom the management clearly did not think was ready for a top 6 role. He makes the bottom 6, still reeling from the loss of MacLeod, stronger.
The Devils single failure was running out of options and cap room (Mercer still needs a contract) before filling out the top 6 forwards. Though the Devils have a very good top 5, that last role will need to be filled by a Tatar or Haula or Palau playing a bit above their current ability-set, at least until the trade deadline.
But looking at the team right now, it's hard not to be very pleased. The goaltending is the best it's looked in years. The blueline is the best in the division to me and maybe even in the entire conference if Luke and Nemec take a big step forward as anticipated. The bottom six is decent, but far better than the disastrous group NJ finished last season with. And the top 6 is still going to score a whole lot of goals. I think we can also add that Keefe should represent an upgrade at head coach over Green and Ruff, who lost touch a bit towards the end.
To me, barring major injuries to major players, this is a very good team going into next season. It's still a bit thin at forward, but the top 5 is terrific and the Devils have clearly strengthened up everywhere else. Maybe Fitzgerald has another trick up his sleeve and can pry McGroarty out of Winnipeg, but it won't be cheap. He also deserves high marks for NOT trading the #10 pick, which adds another franchise-core piece two or three years down the line in Silayev.
I'm optimistic, as I believe we all should be.