*** Disclaimer: Take my answers with a grain of salt, as I haven't played in several months ***
I would have to say herbalism and alchemy. Mining seems like much more of a gamble for money (waiting for arcane stones or whatever they're called and things of that nature), whereas herbalism is a pretty sure shot. Just wander around the desired land picking flowers. The market will obviously change over time, but raiders and pvpers are in a constant need of potions. If they can't make them for themselves or don't have anyone who will make them for them, they will (sometimes...) turn to the auction house. Major Mana Potions sold for a decent amount more than the ingredients required to make them when I was still playing.
I don't think that alchemy is a waste of time (Newton would have agreed with me!
), but maybe that's just me. Playing around with the auction house wasn't something I did much, so I don't have an exceedingly strong opinion about the matter.
From my (minimal) experience in making money, I would say that the best way to make money is to work the auction house. My old boss could start himself off with two gold and make a steady 10-50 gold a day just by working the auction house. There were a few select items he bought from vendors, some he crafted, a select number of ones that he got as loot and, of course, ones that he bought from the auction house to begin with. I was absolutely astonished when he first started doing it. His character was level 16 (legitimately) walking around with over 200 gold!