(Alchemy + Mining) - Herbalism = Profits
Alchemy is a crafting profession based solely on herbalism to level. You can't really get to 600 without it, and you will pay an arm and a leg to do it by buying herbs on the Auction House only. The thing about alchemy though, is once you hit 600, its not really worth pairing with herbalism anymore. Its a funny profession in that it has three separate specializations. Elixir (flask) and Potion spec'd alchemists still rely heavily on herbs to craft their wares, while transmute alchemists (like me) don't really need them anymore. I would go so far as to argue that even flask and pot alchemists don't really rely on herbalism to maximize profits. If you are going to try to corner the flask market, you need a ton of herbs, but mostly, golden lotus. Similarly true for potions but without the lotus and without the large marke for them. (does anyone actually spec this!?)
I can get more golden lotus from my farm in five minutes a day than you can get flying around picking herbs for two hours. Whats more, I can make more gold with mining and alchemy in that extra hour you spend picking flowers, than your flasks would sell for anyways. I perfer to maximise my alchemy profits by pairing it with a miner. Not necessarily on the same character, but having access to both is vital. As with the case of going through mass herbs, you need mass ore to really profit. Basically as much ore as you can possibly get for a reasonable price. Right now, Ghost Iron Ore is obtainable in decent quantities for around 35g/stack on my server, yet Trillium bars are selling for 45-50g each. There is a lot of profit potential in there since 1 stack of ore smelted into bars can be transmuted into a trillium bar through a largely automated process.
Queue up as much ore as your miner can hold and go do something else while it smelts. Mail it off to your alchemist (or have postal do it for you) and click "smelt all" and continue doing something else. When all is said and done, you have AFK'd yourself a 33% profit on some of the most common crafting materials in the game. Being transmute spec'd will only increase those profits. Personally I like the idea of setting the extra trillium procs aside to use for my daily Living Steel transmute. This adds another hundred or so gold profit per day for no work at all. Even more if you craft with it.
According to PTR 5.2 patch notes there is a really good reason to stock up on trillium bars. Wrathion is going to require 40 of them to advance to the next stage of of the legendary questline. This means that as soon as the patch hits (early March I think) demand should raise and with it, hopefully prices. Add to that any new recipes that require lifing steel and we will hopefully see a resurgence in the market. Until that time, if you are going to sell Trillium bars, I would suggest doing so in stacks of six, in addition to any other denomination you chose. This makes it a little easier on Alchemists who don't know the value of a good miner.