The weapon Monstrosity’s Shipbreaker is showing the first new raid boss as the source on your site. That’s wrong, it drops from the boss Radiance of Azshara (according to both Wowhead and the ingame dungeon journal).
We will re-scan data this week, and probably once again right when the raid opens next week, should fix it up. The source information we have is based on the PTR data we scanned just after 8.2 went live.