Worked out ok for Pitssburgh in 2017 when they won a cup. They had 2 of the top 5 centers in the league and a defense that consisted of Letang, Maatta, Dumoulin, Hunwick, Cole and Oleksiak. That isn't exactly a stud defense corps. If I'm not mistaken I think Letang was out in those playoffs due to injury as well.
I agree that it would be better to have a good balance but when a top 10 Center in the league becomes available (which never happens), that doesn't cost you assets, you take it. I would much rather keep the two centers and trade one of our wingers for D if you have to. Wingers are easier to replace than centers. Like if we were to trade Nylander for example, we have Robertson who looks like he can be a good replacement on the 2nd line. He's young and there is no guarantee but a skilled winger is easier to replace than a ppg center. Pitts wingers consisted of Kessel, Guentzel, Hornqvist, Rust Sheary, Hagelin. They were built pretty similar to us.
Carolina in 2006 is another example of a team that had two 1Cs in Staal and Brind'Amour that a D corps that consisted of F.Kaberle , Hedican, Ward, Tverdovsky, Commodore and Wesley. Not exactly a stud Defense.
Again I would prefer a more balance team but not every cup winner was built the same way and those 2 teams show that you don't necessarily need a top tier defense to win. This year having Rielly, Muzzin and Barrie is a great looking top 3 on paper. Barrie will be gone next year but if we had another Muzzin type player on the right side to compliment Rielly that would be a helluva group. They aren't exactly easy to acquire though. A guy like Pesce or Manson for example are guys with huge asking prices through trade. Hopefully a healthy Dermott can progress to where everyone Hoped he would and Sandin and Lilly can turn into good top 4 D men like they're tracking to be on the cheap.