It really depends on what you are looking for, and how durable you believe these guys are. Tanev, if he stays healthy and doesn't decline, will be the best partner Rielly has ever had. OEL provides some secondary PP and is decent as a third pairing guy, can move the puck. Hakanpaa if healthy, is a good third pairing guy with physicality, and is an upgrade on Edmundson.
Tanev, OEL and Hakanpaa are upgrades over Brodie, Gio, Edmundson and Lyubushkin.. At least in my opinion.
Overall defensive play will really depend on Berube, how healthy and durable this group is, and goaltending. We also picked up Myers, Mermis and have Benoit, Webber and Hirvonen... so it's a deep group.
It's a better group at moving the puck, which we certainly needed. Depending on who is in the lineup, it isn't quite as physical... though McCabe, Hakanpaa and Benoit do provide what's needed, if they are all in the lineup at the same time... which seems unlikely.