Just realised that herblore would be super useless considering that all the high level potions are available in the shop.. Which means if you want to make it worth working for it - deleting all the existing potions in everyones bank and I don't think that would be good for pking, lol.
If you add herblore right now, I think the only people who would train it are the ones who care about their spot on hiscores, which are not too many..