Currently herbalism sits in a strange place, a lot of desirable potions simply cannot be crafted but it could easily be made to fill an existing gap and make mundane life just a little easier.
As an example, herbalists can make four potions of giants strength with a handful of reasonable materials for a CL15 potion. That'll last for five times as long as a standard potion. For a mundane who'd ordinarily have to sip every hour, that's a huge leap in quality of life.
It would be an improvement to the crafting skill if it had the ability to craft some or all of the following
All of the zoo potions at CL15 (Much like the existing giants strength potion, but with recipies to cover all of the other types)
Lesser Restoration Potion (These are NPC drops only which make them unusually valuable, as far as I'm aware)
There's probably even more potions it could have in it's list, but I don't really feel like an authority on what would be considered fair. It just seems as though herbalism is largely underutilized.
A step further would be to make the CL15, crafted variants come maximized which would be a pretty big leap in quality of life while warding at the cost of gold and preperation to get them made prior.