I play with 250 - 300 ping from SE Asia and am dying frequently outside a dungeon bosses red circle even though I immediately dodged when I saw it. But to the server, it appears I dodged only after the red circle damage has been activated
My suggestion is to level a boss red circle mechanic based on the highest player average ping so that they are not missing out and dying frequently or having to anticipate the red circle & dodge unneccessarily. Or give players more time to dodge before activating the red circle damages for all bosses in EOS
I also face slow swapping bar and general slower response time for ability activating, but I guess nothing can be done for them. Maybe reconsider "while slotted gives x advantage" abilities so that the client does not need to wait for confirmation from server for swap bar change if that's the reason why client needs to wait for the confirmation from server before swapping the bar