From what you say, you didn't have duplication turned on for all of your folders. (Possibly you didn't have it turned on at all.) That's why you don't see all the files under the DE folder.
As for recovering data from the dead drive, if it were recognized at all, you might be able to use some sort of data recovery software yourself to see if anything could be retrieved. Since that seems not to be the case, your only recourse is to send the
drive out for data recovery. This is, as you note, pretty expensive, and results aren't guaranteed.
I'm not on the WHS team, I just post a lot. :)