I don't know where you're getting the idea that Scandella didn't play with Parayko or against top lines, but it's demonstrably false.
Scandella's most common d partners 5v5 were Dunn (307:34), Faulk (243:55) and Parayko (130:19). His time with Dunn was mostly 2nd pairing minutes when Parayko was injured. When healthy, Parayko was primarily paired with Scandella (130:19) and Krug (126:55), with Walman (86:03) and Dunn (85:49) also seeing some time.
According to PuckIQ, Scandella (143.3) was second on the Blues in TOI played against "Elite" QoC behind Faulk (162.7) and just ahead of Krug (143.1) -
PuckIQ | Woodmoney
Overall, Scandella had a 43.6% oZS% last season, but even that relatively low number is inflated from the minutes he played with Dunn (likely because the coaches didn't trust Dunn in the dzone). According to NaturalStatTrick, Scandella - Dunn had an oZS% of 52.88%. When Scandella was paired with Faulk (43.75%) and Parayko (
31.71%), the oZS% dropped quite a bit and I would wager the defensive assignments where a LOT tougher in terms of QoC (again, likely because the coaches didn't trust Dunn defensively). -
Defensive Pairs - Natural Stat Trick
Was Scandella perfect? No, of course not, and nobody is saying he was. Were Scandella's contributions worth $3.275 mill against the cap? Yes, IMO. Did Scandella eat a lot of tough defensive minutes against other team's top lines? Abso-f***ing-lutely.