I think you need to have two good stay at home dmen in this league that have the ability to move the puck effectively. If you look at the past cup winners, they've had at least two of these types of dmen on their corp. Hawks had Hjalmarsson, Roszival, and Seabrook, Kings had Mitchell, Scuderi, Matt Green, even Voynov, Bruins had Boychuk and McQuaid, and then Chara to an extent.
Coburn -> Effective two way defender who can skate, move the puck, defend top offensive threats in the league, etc
Streit -> Offensive dman, PP quaterback
Schenn -> Physical stay at home dman, who isn't awful at skating and can move the puck effectively on most nights
Grossmann ->Same as Schenn, but a bit slower and a more effective shot blocker
Gus -> Positional two way defender, solid puck mover, and can play the point on the PP
Honestly, this isn't a bad group of defenders going forward. They are missing one more exceptional two way type of guy, who could also be a PP specialist. This is Kimmo's role, and it'll be hard to fill it. Streit probably can't do all the things Kimmo does unfortunately.