To be honest, it is really hard to make professions worthwhile in a MMO.
The only way your products sell is if it is hard to make them:
- Either it is hard to raise the skill (at least to the "worth it" point)
- Or it is hard to get the proper recipes (the one that will interest people)
- Or it is hard to get the components for those recipes
Any of those three will make it frustrating to the average player. A high-end crafter should be like a high-end raider: someone relatively rare and not always found. Many willing, few managing.
So, once your philosophy is that every player should experience any given facet of the game, then profession can't be hard to level, can't rely on hard recipes or too rare components. The latter were both tried by Blizzard at one point, and they apparently failed enough to achieve Blizzard's objectives that they were buried deep, never to be let out again.