From a very simplistic point of view. An NHL team has 1D, 2D, 3D and 4D players on its two top4 pairs. Then you have 5D, 6D and 7D in the mix for the third pair. Let's say, our defense is made of three well balanced pairs 1D-2D, 3D-4D, 5D-6D. X=1+2+3+4+5+6=21. X=21 is the median value for standard NHL defensemen core. To win a SC, we need an X<21. In 2018 Niskanen was 1D, Orlov was 2D, Carlson was 2D, Kempny was 4D, Orpik was 4D and Djoos was 5D. In 2018 our X was = 1+2+2+4+4+5=18<21. We had an OK defense to win a Cup. Today we have: Carlson = 2D, Orlov= 2D, Kempny=4D, Jensen=5D, Fehervary=5D, Dillon=5D, Siegenthaler = 7D.
If you go with the following D pairs:
Orlov-Jensen
Dillon-Carlson
Sieg-Fehervary
your X=2+5+5+2+7+5=26>>>21. This is a TERRIBLE defense not good enough for an NHL team. It has low value. It is terrible. We have to improuve it.
Let's say we can find a 2D to play with Orlov on the shutdown pair. In this case:
Orlov-2D
Fehervary-Carlson
Kempny-Jensen
gives X = 2+2+2+5+4+5=20<21. This defense is much better than the terrible previous one. But not as good as we had in 2018. The only way to have a better defensive core (and we should) is to find 1D and not 2D to play with Orlov and to somehow upgrade Jensen on the third line.
Orlov-1D
Kempny-Carlson
Fehervary-4D
X=1+2+2+4+4+5=18<21. As good as it was in the 2018 Cup run, There is NO place for Dillon or Jensen. Fehervary and Kempny are key pieces as they bring a lot of value at a very low price capwise.
I tried to make it as simple as possible.