I am no expert, but, I have heard (and found)the opposite. At high level it can be useful but at low level it is naff for your own stuff. I had mining and BS on my warrier but dumped BS for JC. BS was well BS I found! I thought that yea great make my own armour but it was so poor and the amount you have to make to up the level is quite huge. If the gear was made soley from ore it would be like ok, I have to make loads but at least the mats are free but NO you have to buy mats to make gear and then you wont be able to sell it for a profit.

Mining/Blacksmith Warrior here, 375/375 in both.
So I know what I'm talking about, basically.

Don't do it. Blacksmithing is an absolute money sink. No profit, the gear you can make isn't worth it and is easily beaten by other, more easily attainable, gear.
I'm dropping it and picking up enchanting so I can make some money.

Please please PLEASE do not take Blacksmithing unless you have a load of gold to spare
and I mean a LOAD of gold.

Don't invest in BS , get mining or skinning will do. Sell all mats gathered and use that money to buy ready made Weap or Armour from AH or crafter. NO HEADACHE !! NO STRING ATTACHED !

As for me, i've chosen alchemy/herbalism. Lot's of people think it's a weird choice, but it's not hard to lvl up and you don't need too many mats from other professions. For BS you need to have mining and you'll end up buying loads of leather, and on higher lvls loads of primals (and it COSTS). Unless you're mace specced warrior and aiming for Stormherald, or your guild needs 375 BS (that's was my case) i don't see any reason to become BS/miner. Surely, BS has some unique stuff at higher lvls, but you'll be able to find the same quality raid drops.
Warrior is heavily dependent on his gear and in case stats on your gear suck, alchemy can help buffing your most important stats (temporary, but very usefull). If your gear is one of the best, some more buffs will never hurt, cause warrior has limited buffs. You'll also have lot's of VERY usefull warrior consumable, like http://thottbot.com/i13442  or health pots, that you won't need to buy. And finally, you'll be able to sell pots and elixirs and you'll be always welcome to the raids and partys thanks to some additional buffs you'll be able to provide.

Mining/Blacksmithing - Make all your own equipment.
Herbalism/Alchemy - Make healing potions and potion buffs.

mining/eng here eng owns cause those bombs and other stuff and u also get jumper cables bad ass looking googles and the helicopter lol eng is fun and it works good if ure a miner

Get alchemy and herbilism as health potions can save you if you have to solo or have no healers in your party.

Or try mining and engineering as you could make bombs and(if you learn to use a gun) you can create scopes to increase its attack.

If you really do want to do mining and black-smithing you will have to train it up really well to get any good gear.