Did you go 30 minutes due to use of raw or uncooked meats in your stuffing? I would think that's way too long for fish, at least a thin filet of sole or other light meat fish. Higher heat and a shorter cooking time is better. It's been a long time since I made stuffed anything-fish, but I don't recall cooking times being more than fifteen or twenty minutes, tops.
If your stuffing consists of things already cooked and/or serve-ready, all you really need to worry about is getting the sole properly cooked. The stuffing only needs warmed to a palatable eating temp.
Brad