All that - ultimately - comes down to him doing what’s necessary. Toranaga uses people based on their talents/purpose and that’s what gives them value to him.
I don’t think the show tried to impress upon us that he’s a “good person”. I mean, the guy let one of his vassals off himself and his baby boy just because he spoke out of turn in a meeting. He’s a man bound by codes and traditions. He’s honorable without needing to be “good”.
He sees value in the Anjin, thus refuses to let him go.
Again, the Mariko revelation was silly to me. She used the “piece of the puzzle part of bigger picture/endure/purpose” speech on Fuji herself - and seemingly was aware she holds a similar role when she did so.
He obviously recognizes the tension between Mariko and the Anjin. They kept bickering during that meeting with him. The sex was likely an attempt to sever their bond. He did tell Buntaro to divorce Mariko, he refused - I guess the next best thing was to make Mariko watch the Anjin pipe that prostitute to create distance between them. He did say he didn’t want bickering in his clan - referring to the love triangle thing Anjin, Mariko, Buntaro got going on.
I’m not saying lady Ochoba’s grudge is completely unfounded. Sometimes people get hurt in the process of doing what’s necessary. I’m just saying I’ve not seen any
shift in Toranaga’s characterization