Having played what I consider the ultimate crafting game and the one thing they did right in that game, SWG, I can totally understand wanting to be able to find your niche. The problem is in a game like WoW that is very hard to do because everything is static so eventually everyone will figure it out or as the above poster mentioned it will hit Wowhead and then your niche is discovered anyways.
I think based on the interviews the goal is separate players somewhat by creating branches that get more an more specific. So as Ion proposed if you wanted to make good armor you would grab armorsmithing, and then you might latch onto say helms to concentrate on. By doing so you could essentially make the best helms in the game while someone else may go down the path of making the best legs, boots, etc.
I’d love to have a system where variables are applied to crafting materials and things, but unfortunately that would require a complete rebuild of how WoW operates at a core level.