I finally gave up on fixing these brews individually and decided to blend them together, which gave me about 3 gallons. I also sat them on top of a bunch of extra herbs - eyeballed amounts of hibiscus, pea blossoms, heather, and elderflower.
It improved the balance of this mess to the point at which it was actually starting to taste well-built, and yet, it just still wasn't my cup of tea.