I have every profession covered by my alts so my account is entirely self sufficient, however I prefer to level the characters individually when I feel inclined to play the class. If I have to level to 90 in order to acquire the mats to max the profession it takes the game play choice out of my hands.
To take it a step further, with the number of alts I have I prefer to take the path of least resistance to max level once I get the main finished.
Anyway as I said, hopefully there are alternative points available through crafting that won't require me to level the alts right away.
In addition to serving as a core crafting ingredient, Spirit of Harmony can also be used to purchase a variety of additional bonuses or materials that your character may need. While not every profession will get equal value out of them, most everyone will need to collect them for one reason or another.
Either way the characters get leveled, some of you just get a little too defensive when anyone questions a change.