One of the best tanking breastplates in the game that is not too terribly difficult to obtain is the [item]Bulwark of Kings[/item]. In order to get it, you first have to craft the [item]Breastplate of Kings[/item]. In order to do that, you need to farm or buy a lot of materials, primarily lots of Primals.
[item]Breastplate of Kings[/item] requires the following:
8 x [item]Primal Might[/item]
8 x [item]Khorium Bar[/item]
6 x [item]Hardened Adamantite Bar[/item]
6 x [item]Eternium Bar[/item]
For the Primal Might, you need 1 each of [item]Primal Fire[/item], [item]Primal Water[/item], [item]Primal Mana[/item], [item]Primal Air[/item] and [item]Primal Earth[/item]. Since you are already a Blacksmith, it is likely that you are also a Miner. Which means that Primal Earth won’t likely be a problem. It is all the rest that can give you a headache.
First off, hopefully you have a guild member or friend who is a Transmute Specialist in Alchemy. This could help save you some time. Have them do transmutes for you if they will. Hopefully they can not only make your Primal Mights for you, but also transmute your excess Primal Earth into Water. With some lucky procs, this could save you lots of time and money.
Farming for the rest of the Primals can be a tedious task. Farm [item]Mote of Air[/item], [item]Mote of Fire[/item], and [item]Mote of Water[/item] at the Elemental Plateau in North East Nagrand. Farm [item]Mote of Mana[/item] from the various Warp mobs in Netherstorm. Another good place to farm Mote of Water is by killing the worms in the lake in Terrokar NE of Shattrath. Obviously get your [item]Mote of Earth[/item] from mining. Mining Fel Iron Deposits will also sometimes get you [item]Mote of Fire[/item] as well.
In addition to outright farming Motes, make sure you run the Daily Quests for Skyguard, Ogri’la, and Netherwing if they are available to you. Use that extra cash to watch the Auction House for low priced Primals and Motes.
Once you have all your primals (you did have your Transmute specialist do the Primal Might transmutes, right?), just craft up the other pieces.
For the [item]Bulwark of Kings[/item] the biggest problem are the [item]Primal Nether[/item]. My heroic of choice is Heroic Mechanar. Not only is it fairly quick and easy to get to and kill the final boss, but you also can get [item]The Sun Eater[/item] and [item]Vanquisher’s Legplates[/item]. Let your group know before the Nether drops that you need it for your Breastplate and if they are willing, roll after the fact and let them know you will buy looting rights if they win the roll. I have had good luck using that strategy. Farm up your 10 Primal Nether and 10 Primal Mana to craft your [item]Bulwark of Kings[/item]! Once you have it, I would recommend gemming it with 3 x [item]Solid Star of Elune[/item] and enchanting with Enchant Chest – Exceptional Health (+150 health) to finish it out! Enjoy