Sorry, no discounts on DCL cruises for being a DVC member. If you book thru member services at least one person on the reservation has to be booked on points. The cash rates are lower than DCLs highest price, but more than their lowest.
When we priced out a Mediterranean cruise with us using points to pay for two children, the cost Member Services quoted us for other passengers was much higher than the price on the DCL website. We would have saved around $300 and used almost 400 points. If we used points for one adult, we would have saved $1400 by using almost 500 points. I do not know if this is typical or just a consequence of DCL lowering cruise rates after the DVC rates were set. But I certainly would not count on saving money by booking through Member Services. If you do get a quote through DVC, check it against the rates you'd get by paying all in cash.
You cannot book totally on cash through MS for cruises as the first passenger must be booked on points. The exception to this has been the DVC Member Cruise which has different booking rules.
You will do far better shopping travel agencies if you are interested in totally booking on cash, anyway.