Today I was crafting some rare Roughspun robes for an alt. After I made the robe I equipped it and attuned it. I looked at the stats and realized that I didn't imbue it.

So I took it off and imbued it, after being imbued it was no longer attuned and I put it on the broker for sale then made a different type of rare robe for my toon.
This works for T2 Rare robes. It could possibly work for anything that is able to be imbued. Essentially you could make rare chest/leggings, wear them till you outgrow them, imbued them then trade them or put them on the broker.