This is something I've experienced in unofficial recently, and so far only after v15. The sheer number of them showing up is disturbing. My friend lost his schooner to getting chased by one, and 2 more pincer-ed him, and then nearly getting cut off by another one. Their levels are all varied so its not a horde of low level SOTD's either. I've also witnessed them while going from grid to grid. There can be anywhere from 1 to 7 in rendering range. It's been more rare not to see one.
However, I'm expressing my experience. My schooner is equipped with a large speed sail, so SOTD have not been as much of a hindrance to me personally.