As far as I can tell, it has nothing to do with lag. My connection can be perfectly fine and I will get hit by a mob that is using a one hit attack. The only consistency I can find when this happens is the damage does around 3/5 of my max hp when it one shots me, its never more and never less. I will literally be at full hp, get attacked for a certain amount of damage, and it will one shot me. I always go back and check my battle log just to make sure I am not seeing things and it is only recording me as being attacked once for the same amount of damage I thought I saw pop up over my head just to make sure I didn't get hit multiple times. Anyways, I would like to see how many more people this has happened to.