Remember when Teutons got given Herbal Medicine for free and people said this buff kinda sucked even though it also increased the base healing rate from 4x to 6x?
Well with the release of Dawn of the Dukes. This tech is actually legitimate. At 200 gold, it's quite astonishing.
Since the Poles unique unit Obuch shreds armour off your units. The only way to get your armour back is to fully heal.
Castles (and Kreposts) regenerate units faster than any other building, and can also heal cavalry which towers and town centres cannot do. At 72HP a minute you can go back to battle in basically 1-3 minutes of healing if you're at 1 hp (depending on your unit).
One could argue an idle army is a useless army and you'd rather have a few monks forward, but a combination of both monks and herbal medicine can actually be quite practical. Especially if you're healing Teutonic Knights or whatever in your castle in a treb war and ungarrison when Obuchs and winged hussar come to snipe.
Maybe its satire, but the devs at FE are so big brain buffing Teutons from day one. Easily S tier now.
Herbal Medicine is the future.