You have discovered the perfect 1-2 punch for making TONS of cash. These two trade skills are by FAR the easiest and fastest way to make money. You don't have to use what you gather/mine and convert it into something else. Let alone mix the ingredients into some other form, ie., blacksmithing and/or alchemy, to get something that you can sell readily. Both herbalism and Mining get you raw materials that are usually far more valuable than anything else in the game. And you get ALL of your 'cash' crops for FREE. No need to ever buy flux, flasks, or other frivolous items. Your cash is up front. You simply sell your raw material on the AH and collect the cash.
Many people will say that you can't mine and gather at the same time, buy these people have obviously never been a miner/herbalist. You get a icon for each trade skill. Simply place both icons in the corner slots, and toggle back and forth between them. Set your zoom out to the farthest setting, and you can gather every herb and mine every node within any zone. Talk about EFFICIENT! You are literally killing 2 birds with 1 stone.
I have personally been a miner/herbalist for over 2 years. I have more money on my chars than I can spend. My bank is in the THOUSANDS. Everyone else complains about not having any money, while I quietly sit back and rake it in. lol