I like to think that Mako and Herc became really close after the cancellation of the Apocolypse. Just as hard as it is to lose a parent, it can be even more devastating to lose a child. And while Herc never replaced Stacker, and Mako never replaced Chuck, they both made time for lunch outings and workouts and games of pool and visiting graves and catching up and drinking contest and bowls of frozen yogurt . Herc would catch himself saying “That’s my girl” every time Mako bested Raleigh in the Kwoon and Mako found herself looking for Herc’s grin of approval as Raleigh wheezed in a heap on the floor.
Hi there! I haven’t written or read any meta for that particular scene suggesting Joan being a drug replacement, but perhaps some of the following Elementary fans can help with that.
elementarymeta's also a great source. :) Sorry I haven't been able to help much, and I hope you find what you’re looking for!