In the current version, it is a necessity to level multiple crafting classes to 45 to acquire beneficial abilities in order to HQ items. We understand that this can be a bit frustrating so the development team did their best with the current system limitations by making edits to crafting actions in patch 1.22 to help alleviate some stress players may be having.
In A Realm Reborn we will be adjusting crafting actions and making it so a portion of them are class-specific so when leveling a single class it will be possible to acquire the necessary abilities to make an HQ item. With these changes, the need to level multiple classes to 45 in order to HQ will be eliminated.