I only craft the ones i cannot find at bazaar and then only if i need them for more crafting. I found it is easier to just buy the cards you need instead of crafting them.
What do you think? I am pretty good in Reagents, But I haven't Crafted ANY Treasure cards yet. Have you? -Heather Willowbreeze, LvL 21, Balance#*
For the lower level spells it is usually better to buy them. Once you need to start using the 5 and 6 pip spells in your crafting, you usually need to craft these.
I craft treasure cards all the time. As someone else said, the lowest levels are easier to buy at the Bazaar to use for the higher level card ingredients, but if you need Nature's Wrath, you are MUCH better off crafting them than trying to buy them.