I used Travel Guard last Spring (recommended by Disney). Luckily, I didn't have to file a claim, so I have no idea how they are on that end of things.
When I took a cruise last year (not DCL), I used insuremytrip.com. I plan to check them out for my next vacation -- not sure if they cover DVC or not, but it's worth a look. They have a plethora of plans and you can select the one that works best for you.
I believe you have to book travel insurance no less than 30 days prior to your vacation.