Well, I met that miniboss in the game, but I thought he acted a little differently, with the shooting...
Oh, and I found a few things: When you face off with the miniboss, no door or anything closes off the room. I fought him and he ended up going up the passage to the left where I had come from. This made it almost impossible to face him without being hit, since I'd have to enter the tunnel at the bottom and he'd spray down the narrow passage, so I couldn't dodge. It might be a good idea to block off the room untill he is dead, also to stop people running away from him. Not necessary though, if you want to keep a more 'underwater temple' idea and less of a 'video game fight' idea. In an underwater temple there are no doors triggered by the life of a being.

Also, the miniboss comes back if you re-enter the room. I'm not sure how you'd fix that though, and I guess it could just be left like that. Just something to think on.
Good luck.
