On tortos, you can multidot when the rockfall happens. The moment the turtles come out, dot them up and you can cast while still moving in time for the rockfall. They don't happen instantly. Also because of your passive dmg reduction there is a good chance you won't lose your shield on the stomp, nice little gain there.
On ji-kun, it's mostly depending on what your role is. We farm it currently with 3 nest clearers, and 3 boss nukers who only go down twice in total for feathers. I don't think we are particularly good for clearing nests. Moving from feed young can be done in advance, when it is happening move before it drops (On dotting or SS proc) and it wont ever bother you. For downfall, stand close to the boss and try to be in an eclipse when it happens. Roar will save you easy mode. Sometimes i use dash aswell, it's only for a few seconds, falling down is way worse
On durumu try to move ahead of the beam. And then cast till the beam gets closer. The openings are always quite big, so run to the most right point and you should be able to get 1-2 casts off. Ofcourse take the melee route, ranged route its impossible to cast.