The thinking was basically that once you master your alchemy,
then you get to learn new tricks. Alchemists of a lower level would still get XP from using those lower level dusts to craft stuff of their current level, and that's how they should use them. But since the main shortage of dusts is in the higher levels (since all the raiders are using those level 60-70 potions/poisons), and since higher level alchemists are complaining they have useless lower level dusts sitting around their bank and they clearly can't gain any more XP when they're already at the cap, the new recipes were aimed primarily at these guys.
The quest, well, we just thought it would be a bit more interesting to quest a book rather than simply having the recipes automagically appear in your level 70 books. And it was a good opportunity for me and Olihin to learn how to make quests (or at least, the very basics). The important part was the recipes, of course.
GU38 will be bringing with it a new quest for level 20+ crafters, as noted in the "state of the tradeskills" post stickied up above. Again, a fairly simple one, but we gotta work our way up to bigger things slowly.
The tradeskill class quests that will start in Kunark are going to be much longer and more complicated, but yes, will require you to be a high level crafter. Currently I'm thinking level 75, although nothing's set in stone yet. They're class-defining quests that should, I hope, be very cool and definitely something to work your way up to.
LINK