It's just matter of dodging shit. While the lag makes this harder dodge boss than in ex. wow, but learn the boss skill rotation helps quite a lot.
https://i.imgur.com/UbacDrh.gif
Have that Gif on your second monitor or print it out or just learn it. Having 2-3 healers + 1 tank is also helping with it. The amount of healers you can bring is evaluated by if you can bring the hearth phase down with 3 or not. The only "dps race" is the hearth phase. After that it's just matter of staying alive long enough.
For the bomb phase those "3 wave" bomb cycles.. Go to middle when they start to come -> When landslide comes, dodge the landslide to the last bomb wave side. And after the landslide has been casted, even if you see bombs etc there, just run to the middle again. No matter what. When the landslide comes, GO TO MIDDLE. You will get hit by the last bomb wave if you do not do so.
Hopefully this helps you and others.