I noticed that the QAR wasn't spawning much since yesterday, so I emailed POTCO about it, here's their response:
Thank you for writing to us about the Queen Anne's Revenge.
There has been a change to how frequently the Revenge is spotted throughout the Caribbean while you should still see it sail from time to time, there will be fewer occurrences from now on.
To take on the Revenge, have a friend, crew member, or Guild member help locate a server, or take on the challenge of defeating LaSchafe when you next see the QAR surface.
I will be sure to pass along your feedback regarding the 17th, when you did not see the QAR appear. If there is a glitch that is not allowing the QAR to sail, we'll need to look into it.
Keep a weathered eye out and let us know if you run into any challenges.
Randy Pirates of the Caribbean Online Member Services