I disagree w/ you saying "you never know". You can say that about any position or team or area on a team.
W/ clear upgrades in Q/Clark/Thompson/Ogboner/Winters/Gary, you're asking for a 3 or 4 players to be injured in order for the upgrade not to work. And then add in promising rooks Downs/Overton/Malachi/Barsham. Can Durant cover? Well, there's a question mark.
How in the world is this not a clear upgrade? Hades, PJ Locke is an upgrade, and he's somewhat of a journeyman. Revel has a year under his belt w/ his top of the league skillset, if he can play then there's another huge upgrade. You never know? No, we do know. We absolutely know that this D has been hugely upgraded.