yea, i have seen some cars that never have wetness at all but still loss some fluid, its going into the brake booster or unto the bell housing.
Since your not loosing fluid and you did a flush and bleed, and im assuming you bled the clutch as well, then it sounds like your master or slave is going out. there are seals in them, little o'rings. They can become damages. typical damage occurs when you bleed the system and push the pedal all the way down where it never travels to and the rust and other crap sitting down at the end get into the seal, it leaks or worse it lets fluid past it causing pedal fade or what your describing.
Bottom line, the issue is the hydrolic control of the clutch. figure out whats going bad.
You can take either end apart and inspect the seals.
Chances are you just have a defective part. I would not go throwing $ at it yet, its worth a few bucks of your time to take things apart and find the cause before you put $ into it.
Then again, taking it to a VW dealership might save you time and $
Dealerships do cost bidding. if the job is not complete and proper function restored they must do the work needed to fix it without charging you more.
If you do go this rough, stand your ground and do not pay a dime more than you are quoted.
I've pulled this trick on really though stuff i know is going to open a can of worms and the dealership ate 4x the cost just to fix it because they just follow orders.
Not sure what else to say but good luck, let us know what you find.