Well im not an expert, but if you compare FFXI with FFXIV you will see that the performance of FFXIV is way bigger if it comes to Graphics f/e. So am i wrong if i would say that the Data that have to be transfered is way more? So that might explain it that like no one had this problem in FFXI before. I didnt had any lag Problems on FFXI either, but on FFXIV i do. It sucks if you run out of AoEs like 3 sec ago and you still get the dmg anyway <.< Only Thing you can do is watch the battle log for faster reaction thats all.
And yeah they talk here about the PHYSICAL data Servers so keep cool guys.