Resale on *any* vehicle after 11 months is sad. If the rapid depriciation in the first year is a problem to someone I would advise to never buy new vehicles. Simply by signing the paperwork you drop the vehicle's value several thousand dollars, before they even hand you the keys...
Those people offering those lower amounts are probably comparing the price to a gas liberty of the same age/miles....
I had a similar situation when selling my TDI Volkswagen recently. People who did not know any better would call me and offer what the gas version was worth... Well below book value trade-in on a TDI... I would just politely say no. One guy tried to convince me that book value was irrelevant.
I simply said no thank you, and waited a couple weeks and a person who knew the value of the TDI came along and paid me full asking price (which was just a hair below book value for private party resale) without batting an eye. He knew the deal he was getting...
People who only know the gas cars just don't get the resale value of the diesel vehicles...
Funny - but not CRD related - story...
A guy who I would bump into at my kids school had a TDI VW just like mine. We would chat about them occasionally. The other day he comes to me and asks if I ever had any problems with mine. I said no. He told me that they had something called the "EGR" clog.
I said, yes - that is a common problem. He was surprised I had heard of it. Their TDI had 36000 miles on it, and the dealership blamed dirty fuel and charged them $300 to clean it and told them that it would be $1500 to replace it and that they would need to soon, and that it was not covered under warranty since it was fuel related.
I told them that a simple adjustment of the EGR parameters using a VAG-COM could drastically reduce the instances of EGR clogging on the TDI, and that also using additives like Powerservice and/or Biodiesel help the engine run cleaner further reducing the likelyhood of problems. I also pointed out how when the EGR valve sticks in the VW TDI you can reach in and flick it open/shut for a temp fix to get you where you need to go. I also told him that it was not an extremely difficult part to clean, that TDIClub.com had all sorts of info about it...
He was crushed - because his wife had panicked and had him dump the car for fear she would be stranded with the kids. They got a Honda Element instead. So some lucky fellow got a 3 year old VW TDI with only 36,000 miles and a freshly cleaned EGR valve - for $8000. Which I thought was funny since I had just seen a 1999 with 165k miles go on CraigsList for $8000... Heck we sold our 2002 with 60k for $12000...
He asked me not to tell these things to his wife, and I told him the next time he has car trouble check the Internet FIRST.

A quick Google search for "TDI EGR" would have saved him lots of heartache.