The quest, The Demon Forge, that rewards the blacksmithing pattern Plans: Demon Forged Breastplate will no longer be available in Cataclysm. If you have a blacksmith and do not know this pattern yet, I would go ahead and complete the quest to get the pattern and learn it. Whether Blizzard removes the recipe itself is yet to be seen. Lately they have removed a lot of patterns from our previously learned crafting recipes, so this recipe may get the axe as well. Once you have this recipe learned, go ahead and farm the BOP demonic runes and craft a few of these excellent leveling chest pieces in case the ability to craft them gets removed. If these are no longer craftable in a few weeks, the value will rise as this is the top leveling chest piece for aoe farming and leveling paladins.
Pally Leveling Uber Gear
The demon forged breastplate is the absolute best AoE farming and leveling chest piece for insanely fast herding and killing of mobs. This chestpiece has a chance to proc a heal-over-time that is also a damage over time spell, basically a drain life type spell. Why is this so powerful? The proc can trigger off multiple mobs at once and it scales upwards with spellpower on both the damage and the healing components. This is even better than before thanks to the new changes with the talent system. All protection paladins get Touched By Light, which adds 60% of their strength as additional spellpower and helps to buff the spell coefficient of the demon-forged breastplate.
In the early days of The Burning Crusade, my paladin would solo farm a mess load of undead in the undead fields with this chest paired with a skullflame shield. You can sell these chest pieces for a nice price, especially if you can snag a skulllame shield to sell as a combo. Attach a shield spike to the shield and you have some serious AoE farming ability. It's so good that when I would lose connection, I would log back in and the 8-10 mobs that were on me when I dropped connection would all be piled up around me dead. You've got to love killing while disconnected. With a little promotion these sell for nice profits and should see much interest on the horde side when the tauren paladins become playable. So learn the recipe, if you don't have it yet, before it is no longer learnable and potentially not craftable.
Paladin Gear Combos
If you are going to level a new paladin, trust me get the uber combo: Demon-Forged Breastplate (with enchant of choice - I like the +heal +mana one for less downtime), Skullflame Shield (with the best shield spike you can get), and a speed enchant on your boots for easier herding. You can solo insane amounts of mobs at a time. Add a weapon with a built in drain effect and /or a lifestealing or crusader enchant and it realy gets crazy. Then if you like this kind of AoE herding, you can grab the Sporegar poisoning shield next. Or if you are ridiculous like me, get all the mobs around you maxed on poison DoTs from the Lichen Shield, then swap back to your Skullflame Shield as the poison ticks away.