Ketsu's leadership stats dropped by 15 points, and this happened before he got tramautized. We know this because he was killed shortly after Rankai's defeat.The author directly stated that he decreases stats if individuals become weaker over the course of the story. he never said a thing about randomly changing his statistics for individuals. I choose to take his word for it. Ketsu by the end was emotionally traumatized. I can see his savvy decreasing because of his mentality.
Shin's emotional boost isn't the biggest boost in the series and he does not go from getting dominated to dominating. He goes from getting dominated to fighting his opponent on an even playing field or slightly surpassing them. Kyou Kai's power boost allowed her to fight evenly with Houken, and Ouki's power boost allowed him to surpass Houken who would normally be stronger than him. baijo's powerboost allowed him to dominate someone who would normally dominate him.Yes I think the guy who can wound Ouki would be able to beat or at least match Bajio. Shin's emotional boost is unsurpassed in the series. He goes from getting dominated to dominating. Your reliance on stats to base your decisions leaves any semblance of agreement between us nigh impossible.
Stats are basically the authors opinion on the strength of the characters, and how strong he wanted them to be portrayed. In rankai's case his stats obviously don't show his overall combat abillity because of his low intellect and lack of speed, but that doesn't mean that we should completely throw them out. Going just by portrayal being able to easilly defeat Rankai would put beast baijo on an entirely different level than the strongest mountain warriors, since it's implied that Rankai could defeat Taijifu, Shuumen and Base baijo pretty handilly.