maybe the solution to limit the amount of classes one character can have ? ( in contradiction to what the game philosophy stand for)

to be allowed to have only two crafter classes on level 50, two on level 37 and the rest only on level 15. this will make hard specialization for crafters and limit the market.
same with gatherer, only one gatherer can chosen and leveled to 50 , the two remaining gatherers will capped on 15. because god forbid a single player will put three types of HQ mats on sale.

and if we speak, then the same with battle classes.
if you chose to play disciple of war, you can have one class to 50, rest of disciples of war to 30 and disciples of magic to 15.
same for disciple of magic: one class to 50, rest disciples of magic to 30 and disciples of war to 15 only.

this will remove the uniqueness of the game, but will definitely solve the whine in this thread.