It's hard, because there's obviously no love lost between the Regent and Shen Wei, but the Regent disapproves of Ye Zun pretty strongly, too. He was upset when the Deacon killed the old Dijun, and he's talked about Ye Zun's troublemaking a lot before, and tried the siege squad. I really do wonder if he's just been biding his time, hoping the Envoy would come and set things to rights -- but when the Envoy does show up, his powers are weakened, oh no!

Yes, this, exactly! And, you know, with some help Shen Wei might still win that fight - but the Regent isn't doing anything to help. (Surely even if he himself has zero useful abilities, he'd be able to instigate something? He's good at being sneaky after all ...)