Li's slash needs to be dodged so getting practice just standing out there and dodging it will help you survive the encounter. There are two ways to time your dodge, either when your circle is half full or when the visual indicator on the ground for the slash goes away. Many times I run into people bringing their damage circle into the safe zone so getting used to just dodging the slash every time lets you avoid that damage when faced with needing to run out to the slash zone. Also, the green circle will always be on a player. This green circle will follow them around. That is why it was out in the slash zone, a player brought it there. It is another reason why the green circle should be focused because if ignored it will just down the player it is on. I will often see the person with the green circle quite far from the group so I will leave the safe zone even though I don't have a circle, dodge the slash, and then be close enough to help with the green circle.
The encounter always has the same sequence of slash -> circles explode -> green circle explodes.