Ancient Leshen Decoction in unmodded game is bugged and instead of providing stamina regen bonus on each sign use it does something like this:
alt-aard - 2 or 3
alt-quen - 2 or 3
alt-igni - 2 or 3
axii - 4 or 5
alt-axii 4 or 5
all others - 0
bonus stamina regen points.

With my mod each use of a sign grants 2 or 3 points of stamina regeneration (every other use grants 2).
I don't think getting 3 points is intended but that's something i could not figure out how to change. But at least each sign grants same regen bonus (:


Installation
Download a mod and unpack it to "path\to\The Witcher 3 Wild Hunt\mods\" directory.