There are three ways to learn alchemy recipes post 300 that don't involve learning them from a trainer. Of the three listed below, only one was introduced with the Burning Crusade. For those of us who played before BC (walking uphill to Molten Core, barefoot, in the snow), vendor purchases and drops are well known.
Be aware, some of the vendor recipes are tucked away in bizarre corners of Azeroth and most are on a timer (limited supply). Some of these can fetch a huge return at your local Auction House. I'm looking at you Frost Oil Recipe.
- Vendor Purchased - Some recipes are purchased from a vendor other than your trainer. Some will require a certain level of reputation with the vendor's faction and some will be available only in limited supply.
- Discovered - Some recipes will be learned because your character has a "Eureka" moment and "learns" how to make something completely different. Between my two characters who are alchemists, I've made a fair number of discoveries.
- Drops - Some recipes are drops from mobs that are killed either insider or outside of an instance. Some will be static drops and some will be the bind-on-equip drops that can drop from any number of mobs.
So, without further delay, here are the drops that you can farm just by killing certain mobs in the game.
There is only one static drop in Nagrand and it comes from the Vir'aani Arcanists around Oshu'gun. These are the casting mobs who like to chain arcane missiles. The level of these mobs is mid 60's so, anyone who can easily take these on can get this recipe. Coincidentally, they drop the recipe for Major Arcane Protection Potion.
Blade's Edge Mountains
There is also only one static drop in Blade's Edge. This one will require a flying mount as the mobs are up near Ogri'la. The Abyssal Flamebringers drop the Major Holy Protection Potion recipe.
Shadow Moon Valley
There are four static drops in Shadow Moon Valley. This is a 68-70 zone but everything is reachable without a flying mount.
- Fel Strength Elixir Recipe - dropped in the area of Legion Hold.
- Major Shadow Protection Potion Recipe - Also dropped near Legion Hold, specifically by the Shadow Council Warlocks. Farm this with the one above.
- Fel Regeneration Potion Recipe - Dropped by a number of mobs in the area of the Deathforge.
- Fel Mana Potion Recipe - Hunters love this as there is no side-effect for them. The recipe drops from mobs in the Eclipsion area. These mobs will also drop Scryer paraphernalia.
The second boss, Captain Skarloc, in Old Hillsbrad can drop the Ironshield Potion Recipe. This, and the other instanced drops are not as "farmable" as the recipes that drop from the mobs above. He can drop this in both normal and heroic mode.
The final boss in Mana Tombs, Nexus-Prince Shaffar, can drop the recipe for the Major Frost Protection Potion. It drops in both normal and heroic, but heroic has a higher droprate. (Heroic MT can be a real pain though)
Sunseeker Astromages can drop the Major Fire Protection Potion Recipe. There are a limited number in the instance, however more than the ONE in the other instances that drop BOP recipes. Still, being exalted on my alchemist priest, I've seen this drop exactly one time. Again, both heroic and normal can drop this.
So, to the alchemists out there, if you don't have these nine recipes, it looks like you've got some work to do.