Let me first outline Hisoka conceptually. While he is primarily a simple hedonist who goes to greath length to satisfy his desire and pursue his brand of 'pleasure', the way this almost 1-Dimensional baseline manifests within the story is insanely convoluted and complex 
This will be an analysis largely focusing on how Tooru is constructed and implemented into the larger, series-spanning exploration of causality Araki has been conducting. I will also be dissecting his psyche and particularly his cryptic behaviour and dialogue
Before I get into it for real, I just want to clarify: I don't think this change in feel and look is something that just happened, I think it was very intentionally designed and worked towards, and I think the series has more than enough elements to substantiate this assumption
To start with the very basics I think Itagaki does a brilliant job of bringing Baki's character to life by using his body as a kind of history book itself, every scar tells a story, each story something we witness in detail within the series. Lots of love and detail put in here 
The past 3 chapters have shown me what the deal with Jack's character is and how he is contextualized in the symbolic framework of the series. I was confused because Yujiro has clear parallels to the Buddha and Baki to the Buddha's son, Rahula (will address in future threads)