Skinning is great is you know what to sell. Leatherworking not so great, in fact i only use it to make the heavy leathers and sometimes leg enchants... Herbalism is good, but the herbs spawn rate is much slower than the ore spawn rate... So, unless you're gathering herbs to craft something (like potions), it's better to farm ores and sell them raw.
If you can get a private buyer, it will be awesome, since you won't put a single piece of ore in AH. I farm between 100 and 200 stacks per day, and i don't have active auctions... EVER.