While I have nothing in principle against crafting plans dropping from out in the world (or even dungeons/raids, although that can be a problem for some) I do object to them being made extremely rare drops.
Somebody put up an order on one or my servers for Temporal Spellthread. I didn’t have it and researched it, to find it was on wowhead indicating it dropped from a very few mobs out in the world (with an extremely low drop rate of 0.3%) or from a Time-Warped Treasure from Uldaman (I am presuming the original version of the dungeon) with a slightly larger but still terrible 0.6% chance.
I have to wonder - why make things like this so damned difficult to get? Why put them in the game and make them almost impossible to find? And if they are found, its more profitable to put them on the AH for extremely high prices (there is one, and one only, pattern on my local AH for 90k gold).
If I could talk to a dev working on professions for TWW, I would ask of them to PLEASE stop doing this. Want to have some things that are harder to make? Then make the materials such that you need to work out in the world at collecting them. But make the playing field for being able to craft them the same for everyone.