Streit doesn't have the defensive defenseman he needs. He's lagging.
Parenteau doesn't have a proper second line center. He's lagging when not with JT.
Jurcina is a tough defenseman with size who lacks a speedy defensive cog to cover him and help dish out punishment. He's lagging.
Nielson has Grabner but needs a Shawn Bates winger who can score. He's lagging on offense.
The team isn't built right. Snow got all the wrong guys save for Pandolfo, MAYBE. Would Streit look better with a defensive Gary Nylund type. Maybe he improves and trading him would be foolish. Parenteau gets paired with Strome next year and he has a skilled scorer who can set up. Maybe he duplicates his play on Line 2 and trading him would be foolish. Jurcina gets help on his D pairing and a coach/roster that encourages toughness and Jurcina is a solid roughian far better than Cairns.
The point is, we're discussing trading talented guys who are being forced to play poorly because we lack a GM or owner who know how to run a hockey team - or are willing to.
There's only so much of this you can blame on having a bad partner. His deficiencies run much deeper than that. He also managed to play well with pretty much the same surrounding players the first year, and the latter half of his second year. That suggests it's not the folks around him, though they hurt, it's him. Streit is poor defensively, and that is simply a bad attribute in a defenseman. If he was 20 you'd know you could work on it with him, but he is long past that point, and due to age, only getting worse. Trade him this year while he still has value.