The phone situation is tough to deal with. I'm by no means a telephone system expert but I've worked for a couple different companies who had sizable call centers. Management of the phone system fell under my responsibilities.
DVC has about 150-200 phone reps on staff. Normally they don't all work at the same time, but cruise booking day is all hands on deck.
Problem is the call volume on cruise booking day is just enormous compared to a typical business day. The Disney Dream has over 1200 cabins. There could be 1500 people calling right at 8am. With many people calling on 2-3 phones, the call volume could be 5000 or more.
There are phone systems which can handle that capacity, but it doesn't make sense for DVC to have a system which can handily accommodate it.
To borrow a Jim Lewis phrase

you don't build a church for Easter Sunday. Given the fact that DVC is spending our money (dues), I don't think it would be wise to spend 2-3x as much on a more elaborate phone system just to accommodate a once-per-year event.
Most people get through the queue without incident but given the volume, I think some fallout would be very difficult (and costly) to avoid. Some problems will be rooted in human error--like the prior post--which a better phone system and more phone lines wouldn't fix.
All of that said, I think DVC is crazy to accept bookings for TWO cruises on a single day. That alone has the potential to double call volume.
Unless DVC has taken steps to streamline the booking process, this could turn into a real comedy of errors with callers trying to book 2500 cabins in a single day. We'll see...