okay, this does take some practice to do,
in gruul fight, gruuls will do a knockback and a shatter, which does up to 7.5k damage to everyone around you,
well you can avoid the damage from others by simply moving away, somtime this is difficukt tho, but you can avoid this damge ny jumping on a part of the wall about 10-15 feet from the right side of the door, does take a few jumps to get up there but it works nicely.
there is also a few other ways i you can avoid getting killed by shatter, but they are just hints not exploints ( just gonna throw these in, if you cant get the rrick down)
1. most raids are so busy trying spread out from each ther they fail to realize the door is completely vacated 90% of the time so just run to the door and chill.
2. you can use float effects during the ground slams, slow fall. levitate, parachute cloak ect,
3. or you can be a cheater rogue like me and use Cloak Of shadows ^_^