IMO, I think DC may be effecting resale prices also. People who are buying these know that in order to exchange them they must pay the annual II fee and exchange fees. Sure they had to pay these before DC but knowing that they are now free for DC members and the potential loss of Marriott inventory in II is probably hurting resale prices further. They are no longer appealing as traders.
For someone looking to buy a home resort to use every year, the deals will be great.