I've worked in data centers for most of my career and I'm an avid gamer. I can say that it doesn't appear to be a server problem or a network capacity problem since the lag is so low. That leads me to believe it's simply a metric problem. Or to be more accurate a philosophy. What I think is going on is Square Enix is keeping the numbers of players per server low in order to keep playing quality high. the servers are being slightly UNDER utilized intentionally By SE. For what reason I have no idea. But I have about 20 years experience giving me this hunch.