The recipes that drop from trash in Firelands have had their drop rate nerfed in a recent hotfix:
This makes sense from a design perspective; these patterns take some pretty rare boss drops to be made and produce gear on par with normal mode Firelands boss gear drops. On most realms, everyone who is getting the recipes is trying to sell them -- at first, for a lot; however, I've been picking them up for a tenth of what they were being listed for yesterday.
One of the interesting artifacts of this system before the nerf was that the people most likely to get the recipe were people farming reputation by doing trash runs. The people most likely to be able to craft the items were the ones in the more organized and progression-minded raiding groups. Now that the drop rate has been reduced, in a few weeks when more guilds are making it farther into the instance, it's possible that more recipes will drop into the laps of raiding guilds than trash PUGs.
Click past the jump for a list of the recipes that are affected.