Once upon a time, it was just as common for a full room to die as an empty room during dormancy. I think we got it changed so a full room is less likely to die - but the chances of death for a room with 5 or 10 isn't that much different. You shouldn't be harvesting during dormancy at all (or the month before) if you want them to survive.
However, they are supposed to also:
1) Have a higher chance of growing back the next month, and
2) If a room is full, have a higher chance of "spreading" to nearby rooms.
This is why bigger areas, unless intentionally stripped, tend to recover. Swamps suffer from being small and also constantly harvested, which ends up with them not having as much chance to thrive.
Lastharvest was added to the game to stop strip-harvesters from being able to deplete herbs entirely and stay anonymous.
The mechanic around dormancy/decay of herbs in general is not engaging. Why can't they be hardy enough to never completely run out. Recently i used nature's gift to regrow horehound in almost the entire balach swamp, an area that sees no melds - is it normal for an entire area to lose so many of the plants during dormancy? if so, the mechanic is ridiculously broken because it really wouldn't matter too much if you left 5 or zero (personally i aim to stop at 10, though group harvesting makes that more tricky to hit spot on) as you'd likely lose every one anyway. Maybe someone who knows the behaviours more comprehensively than i could elaborate on whether that is normal of dormancy.
tl;dr limited resources are already unfun and herbalism is slow and arduous, making a way to just not deal with lost herbs at all would be great. X number regrow per day, no matter what. Everyone wins!
It may also be worth considering whether the herb growing mechanism adds enough to the game in comparison to the headache.
If not it seems like you could potentially do something like make it that peak months refresh the herbs nodes to full even if they've been stripped and fiddle with numbers like the maximum that can be in one spot at once. Which would shift herbs slightly to be, if you can see it then it's fine to harvest.
These kind of feel like they'd be more interesting in a gold auction - hoping to see them thusly placed in the future, but intrigued to see how they'll fare among credit bids this go around.
I'm not super good with words, but I love you and you're a light in many people's lives! I'm happy I've gotten the chance to know you and here's to many more adventures, yeah?