Hey there @ThatNeonZebraAgain,
All achievements are character specific, however the dyes you unlock are account-wide.
ThatNeonZebraAgain wrote: »Thanks for the reply. Unfortunately, that's what I was afraid of. It seems like since I have my crafting professions spread across 3 characters (eg provisioning and alchemy on my main, then woodworking and enchanting on one alt, and clothing and blacksmithing on another), I'll never get many of the crafting-related dyes/achievements
The Truly legendary requires the same character make the item and the glyph. I don't think the same character has to improve the weapon to legendary. Will test that soon.
Wait, what Achievements are you referring too? None of them are such that you can't easily get all of them on all 3 of your crafters. Or just one of them on one line. The Motif ones will be done by at least one of your crafters at some point. All of my crafters have gotten the Master Refiners and Master Deconstructer's achievements (deconstructing is the best way to gain inspiration experience in crafting, not making things and hence the best way to level a crafting skill). So, you can get almost all the achievements, and their dyes, even if you have 6 crafters. Although the Grand Master Harvesting one might be better if you dedicate one character to farming (which is what I do anyway its easier that way by giving one character all the Keen Eyes)
http://eso-fashion.com/dyes-by-achievement/
The only one I am not sure about is the Truly Legendary, which is to make a Legendary Armor and apply a Legendary Glyph that you make to it. But, you might be able to just do the upgrade to Legendary with the Enchanter, then apply the glyph they make.