IMO, the easier times to book the WDW
DVC resorts include January, 1st two weeks of February, May & September. The summer months are next, followed by the rest of February, March & April. October - December are generally the most difficult. There are periods that are especially difficult and those include the week between Christmas and New Year's and the weeks before and after Easter.
Some room types and views are difficult all year - standard view and guaranteed view at the BWV, and the Grand Villas (3 bedrooms) anytime.
All tht said, difficult doesn't mean impossible or that you must have the home resort booking advantage to make a reservation. Difficult to me just means that if you want to be absolutely sure of getting your first choice of resort, dates, room size and (in some cases) view, you need to book as soon as the 11 month window opens. It doesn't mean that a member without the home resort booking advantage can never book the more difficult times. You will often read reports of someone getting something that is supposedly difficult at the last minute. Waitlists do work for many (but not all).
IMHO, the most difficult reservation to get is a standard view room (any size) at the BWV for the time between Thanksgiving and the middle of December. Unless you are a BWV owner and willing to call at 9 am Eastern day by day, you cannot be sure of getting the days you want. (I hate having to use the wailist and don't like to change rooms in the middle of my stay).
HTH.
Best wishes -