@OP Lag can effect your response time but one way to work around aoe range is after you know the range of it, meaning after you see it used then you can compensate by speeding up your reaction to it just by a few seconds until you get it right.

You mentioned that you are repeating the same challenge so that would mean you have repetitively tried to avoid the same aoe from the same mobs so your chance of predictability should be higher. Make sure you have your chat log set to filter out unneeded messages, even if you have to dedicate a specific chat window to only show mob action messages, so that you can see the aoe attack's action message and the timestamp. It should show you where the mob is preparing the attack and how much time you have to escape after that message is posted in the log. It is a matter of compensating for timing once you have experienced the aoe range.