I think any improvement you make to your roster has a trickle down effect to the other areas of it. And the bottom six is the part that is by far the easiest and cheapest area to tweak between now and training camp. It requires no additional roster movement.
People are still reacting to a playoff run that's now three months in the past. What happened then doesn't necessarily continue to happen in the future. And has been stated a dozen times already, this exact tandem won 50 games last season.
Stuart Skinner is a 24 year old goalie. And Jack Campbell is a goalie that was trending as a slightly above average starter before last season. More likely than not, you're getting an improved result on last season from them. Especially if the team in front of them makes their job easier.