Originally Posted by
Azazello
One of the issues here is that the hit determination is made before the relevant damage animation takes place, and the damage coming off your HP bar is actually synced with the latter rather than the former. It was a conscious design choice on SE's part, but yes, you can sometimes run a long way out of an AOE zone and then see yourself taking damage. It's not your computer or connection, it's the way the game is. It's not that you're actually getting hit outside of the AOE zone, it's that you were inside the AOE zone when the game determined you were hit... as much as 2 seconds before you actually see it register.
That issue is actually a peripheral issue to something more serious, which is cast bar, AOE circle, ability animation, and hit determination syncing, where you can be out of the AOE circle/cone/whatever before the ability triggers but still get hit anyway. This was something that was brought up in beta, got a response from Yoshi-P, and unfortunately was not fully resolved for all AOE abilities. SE is aware of the issue and they already addressed it to their satisfaction. It's highly unlikely at this point that they will ever revisit it.
My advice, unfortunately, is to let it go. Despite the fact that you know it's happening and can even prove it with video evidence, the thousands of people who will blame you for imagining it or that having a shitty computer and connection will sap whatever enjoyment you are getting out of the game. SE is satisfied, the customers they care about are satisfied, that's pretty much the end of the story. If it truly is preventing you from completing content, and that makes you not want to keep playing, then it's time to look for another game. Others no doubt will join you as the same issues contribute to their eventual disillusionment as well.