Interesting little Trick for Lord Ryolith:
Turn on "Track Humanoids" when fighting him. you'll see a Friendly green dot about 60yds ahead of Rhyolith that indicates the direction in which the boss would move if you'd stop all damage. It seems to be an internal helper that Blizzard uses to implement the mechanic and for some reason it shows up when tracking. It's mostly useful to navigate the border of the island and to avoid oversteering when doing really sharp turns. As Volcanos don't show up on the minimap, you still have to aim normally for them.
Enjoy!