Looking at pretty much all the production crafts, save for Alchemy, I'm not sure why anyone bothers. There are a FEW good items in each craft, but I honestly don't think most of them are worth the investment. Dark Iron (Smithing) gear was good for guilds getting through Molten Core, as was Flarecore (Tailoring.)
Well, I'm dropping Blacksmithing and Mining on my Paladin because I've come to realize how unlikely it is I will ever make myself an item that is better than something I can get in a dungeon or through a PvP system. Granted, there are a few truly great items, but they take a really epic level of work to achieve them, and as a casual player, I honestly don't see myself ever putting Sulfuras or Thunderfury levels of work into getting an item.
Herbalism/Alchemy it is for my Paladin; at least potions (resists & mana especially) will be useful for both my Paladin and Warlock. I had a 26 Druid alt that I no longer play that was my alchemist, it was handy having it around.
As for my main, I dropped engineering and am re-learning tailoring because I found myself never even really using engineering, and I wasn't bothering to make more grenades for PvP. Engineering didn't appear to hold anything useful for my caster class in the expansion, so I'm sticking with my 300 Enchanting and soon to be 300 Tailoring. I'll love the netherweave nets and spellweave I can put on my clothes.
Edited, Jan 15th 2007 3:27pm by Sanvyn